CN1315013A - Optical pulse generation using a high order function waveguide interferometer - Google Patents
Optical pulse generation using a high order function waveguide interferometer Download PDFInfo
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- CN1315013A CN1315013A CN 00801155 CN00801155A CN1315013A CN 1315013 A CN1315013 A CN 1315013A CN 00801155 CN00801155 CN 00801155 CN 00801155 A CN00801155 A CN 00801155A CN 1315013 A CN1315013 A CN 1315013A
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Abstract
An optical pulse generator having a high order transfer function that comprises a first and a second nested interferometric modulator, each modulator comprising an optical input, an electrical input, a first arm, a second arm and an optical output. The second interferometric modulator is optically coupled into the second arm of the first interferometric modulator. The optical output of the first interferometric modulator generates pulses at a repetition rate that is proportional to a multiple of a frequency of an electrical signal applied to the electrical input of at least one of the first and second interferometric modulator and at a duty cycle that is inversely proportional to the order of the transfer function of the optical pulse generator. The multiple may be any integer equal to or greater than one.
Description
The generation of relate generally to light pulse of the present invention especially, the present invention relates to the generating means and the method for burst pulse.
The generation of narrow light pulse need be in mass communication and sensor-based system equipment.Narrow light pulse is the very little light pulse of the shared time interval, in other words conj.or perhaps the light pulse with rapid Strength Changes that is produced by control signal.In telecommunication system, when the Strength Changes of modulation format requires to grow out of nothing, and in the time cycle of a bit, arrive nothing again, this will use the light pulse transmission.The generation of this light pulse comprises clock or data-signal.
(RZ) data that make zero are meant or no datat accounts for the data of half bit period greatly.Non-return-to-zero (NRZ) data then refer to have light or unglazed data to account for whole bit period.Fig. 1 illustrates sequential Figure 10 of prior art: clock 12, NRZ data 14, RZ data layout 16.These data layouts can typically be set up in electric system by the logical between clock and the data itself.
Under the situation of high data rate, it is difficult relying on photomodulator of the prior art to produce pulse in the mode of electricity.Producing special applications also is very difficult in the pulse with reservation shape of the narrow light pulse form that resembles orphan and other long Distance Transmission.
Exist several generations to have the pulse producer of the narrow light pulse of predetermined format in the prior art, comprise that the cascade of Mach-Zehnder interferometer repeats.These existing apparatus have used separation FEEDBACK CONTROL part.The input signal of aggregation device and operation bias state are controlled by various designs, the calibrated input signal by each part of aggregation device that has produces needed train of impulses, other the then transition function of modulationmodulator partly, the equipment of use such as electroabsorption modulator is to produce fast-pulse.
Existing design has many defectives.For example these methods all need the time delay and the phase place of varying input signal are accurately controlled, this not only be difficult to accomplish and also cost very high.In addition, produce the higher relatively power back-off of physical size needs of some two-forty signals and increase equipment.
Modern Communication System need produce the apparatus and method of narrow return-to-zero pulse, also needs the pulse of the very narrow bandwidth that produced can grow Distance Transmission.Also need to produce Gauss, promptly a hyperbolic ecant square form height rapid pulse dashes, and that is to say the apparatus and method of the algebraically shape that is used to produce soliton pulse.
The present invention relates to comprise the pulse producer of high order function waveguide interferometer, its generation has the special applications of reservation shape in the burst pulse that resembles orphan and other narrow light pulse form.Primary discovery of the present invention promptly is that nested and parallel interference modulator of setting up can satisfy special applications and have the burst pulse of reservation shape in order to generation.
Correspondingly, the present invention is a feature with the optical pulse generator with high-order transition function.According to an embodiment, optical pulse generator comprises first and second nested interference modulator, and each modulator comprises a light input end, an electrical input, first fen arm, second fen arm and a light output end.Second interference modulator is optically coupled to second fen arm of first interference modulator.The light output end of first interference modulator produces pulse with the repetition rate that is proportional to electric signal frequency multiple, this electric signal inserts at least one electrical input of first and second interference modulators, and duty of ratio is inversely proportional to the exponent number of the transition function of optical pulse generator.Wherein cycle period can non-linearly be inversely proportional to the exponent number of the transition function of optical pulse generator monotonously; Multiple can be to be equal to, or greater than any integer of 1.A phase-modulator can be coupled in series to the output terminal of first interference modulator, with the modulation signal linear frequency modulation light pulse that inserts the phase-modulator electrical input.
According to one embodiment of present invention, pulse producer also comprises one the 3rd interference modulator, and it comprises first, second a minute arm and electrical input.The 3rd interference modulator has an input end that is optically coupled to the first interference modulator output terminal.Pulse producer among this embodiment also comprises one the 4th interference modulator, and it contains first, second a minute arm and electrical input.The 4th interference modulator is optically coupled to second fen arm of the 3rd interference modulator.The light output end of the 3rd interference modulator produces pulse with the repetition rate that is proportional to electric signal frequency multiple, the electrical input of at least one of this electric signal access the second and the 4th interference modulator, and duty of ratio non-linearly is inversely proportional to the exponent number of the transition function of optical pulse generator.
Interference modulator can be amplitude or phase-modulator.In another embodiment, interference modulator is the Mach-Zehnder modulator, and it is formed on the lithium niobate substrate, can be X cutting or Z cutting.Interference modulator also can possess speeds match or temperature compensation function.
According to one embodiment of present invention, interference modulator is a narrow band modulator, and just the bandwidth of modulator is limited in the bandwidth basically.Use narrow band modulator can increase the efficient that light pulse produces.In another embodiment, the split ratio (splitting ratio) between first and second of at least one interference modulator fens arms is less than 1.
Also the optical pulse generator of tool high-order transition function is a feature with the interference modulator that comprises a plurality of parallel opticals connections in the present invention.In a plurality of interference modulators each all comprises first, second a minute arm and electrical input.The optical pulse generator of tool even rank transition function also contains the optical waveguide that connects with a plurality of interference modulator parallel opticals.Light output end produces light pulse with the repetition rate that is proportional to electric signal frequency multiple, and this electric signal inserts in a plurality of interference modulators the electrical input of at least one, and duty of ratio non-linearly is inversely proportional to the exponent number of the transition function of optical pulse generator.Its medium multiple can be to be equal to, or greater than any integer of 1.
The output waveguide of at least one can comprise a bias electrode in a plurality of interference modulators, is added in the phase place of the voltage correction transmission light signal of at least one in a plurality of interference modulators on the bias electrode.In addition, a phase-modulator can be coupled in series to the output terminal of first interference modulator, with the modulation signal linear frequency modulation light pulse that inserts the phase-modulator electrical input.
The present invention also comprises the method with the nested interference modulator generation of high-order light pulse.The method can produce special applications with reservation shape in the burst pulse that resembles orphan and other narrow light pulse form.This method comprises the reception input beam and is separated into first and second light beam; Transmitting the material of first light beam is setovered to change its characteristic by electric light.The extinction ratio of electric light biasing can change pulse.
Second light beam is separated into the 3rd and the 4th light beam, and at least one the material that transmits in the 3rd and the 4th light beam is setovered to change the wherein characteristic of at least one by electric light; Modulate in the 3rd and the 4th light beam at least one with electric signal; The first, the 3rd and the 4th light beam is interfered to produce light pulse, and the repetition rate of light pulse is proportional to the frequency multiple of electrical modulation signal, and pulse duty factor non-linearly is inversely proportional to the exponent number of nested interference modulator.
In the careful description of the present invention and claims.Above-mentioned advantage of the present invention and further benefit will clearly understood with reference to the following drawings and on the basis that describes in detail:
Fig. 1 illustrates in the prior art sequential chart about clock, NRZ data and RZ data layout.
Fig. 2 a illustrates the sketch of Mach-Zehnder interferometer in the prior art.
Fig. 2 b illustrates according to the transition function between modulator access modulation signal and the output intensity in the prior art shown in Fig. 2 a.
The time domain output signal of Mach-Zehnder interferometer shown in Fig. 2 a when Fig. 2 c illustrates with sinusoidal signal access input electrode.
An embodiment of narrow-pulse generator when Fig. 3 illustrates according to the present invention with the exponent number N=2 of nested modulator configuration.
Fig. 4 illustrates the transition function that inserts among the narrow-pulse generator embodiment of the present invention between modulation signal and the output intensity.
Fig. 5 illustrates that generator among the narrow-pulse generator embodiment of the present invention is biased at light intensity maximal value place and the time domain output signal when having the sinusoidal modulation signal input.
An embodiment of narrow-pulse generator when Fig. 6 illustrates according to the present invention with the exponent number N=3 of nested modulator configuration.
An embodiment of narrow-pulse generator when Fig. 7 illustrates according to the present invention with the exponent number N=4 of nested modulator configuration.
The general embodiment of narrow-pulse generator when Fig. 8 illustrates according to the present invention with any exponent number of nested modulator configuration.
An embodiment of narrow-pulse generator when Fig. 9 illustrates according to the present invention with the exponent number N=4 of nested modulator cascade structure.
Figure 10 illustrates an embodiment according to the present invention's narrow-pulse generator with the exponent number N=4 of nested modulator configuration and when a phase-modulator is arranged.
Figure 11 illustrates an embodiment according to the present invention's narrow-pulse generator with the exponent number N=4 of nested modulator configuration and when a plurality of phase-modulator is arranged.
Figure 12 illustrates an embodiment according to the present invention's narrow-pulse generator with the exponent number N=4 of nested modulator configuration and when having to be positioned the phase-modulator of its passive minute arm.
Figure 13 illustrates the general embodiment according to the present invention's narrow-pulse generator with any exponent number of nested modulator configuration and when a plurality of phase-modulator is arranged.
Figure 14 illustrates according to extinction ratio and pulsewidth among the embodiment of 2 * 20Gb/s pulse producer of the present invention as the function of driving power.
Figure 15 a illustrates the light output that is produced according to 2 * 20Gb/s pulse producer of the present invention when driving power equals 30dBm.
Figure 15 b illustrates the light output that is produced according to 2 * 20Gb/s pulse producer of the present invention when driving power equals 27dBm.
Figure 16 a illustrates the light output that is produced according to 2 * 20Gb/s pulse producer of the present invention when symmetrical bias voltage equals 0.2V-pi.
Figure 16 b illustrates the light output that is produced according to 2 * 20Gb/s pulse producer of the present invention when the extinction ratio bias voltage equals 0.15V-pi.
Figure 16 c illustrates according to the extinction ratio of 2 * 20Gb/s pulse producer of the present invention function as the extinction ratio bias voltage.
Figure 17 illustrates according to optical loss and pulsewidth in 1 * 40Gb/s pulse producer of the present invention as the function of driving power.
Figure 18 a illustrates the light output that is produced according to 1 * 40Gb/s pulse producer of the present invention when driving power equals 31.75dBm.
Figure 18 b illustrates the light output that is produced according to 1 * 40Gb/s pulse producer of the present invention when driving power equals 27.5dBm.
Pulse producer of the present invention comprises high order function waveguide interferometer, and its generation has the special applications of reservation shape in the burst pulse that resembles orphan and other narrow light pulse form.The device that has several use high order function waveguide interferometers in the prior art discloses a kind of parallel interference modulator of setting up such as the U.S. Patent No. 5101450 that belongs to Olshansky, and it is used to eliminate second order intermodulation distortion in analog communication system.
At periodical Lightwave Technology (Vol.10 No.8, in August, 1992) goes up in the paper of delivering by Yu Wang-Boulic that is entitled as A Linearized Optical Modulator forReducing Third-Order Intermodulation Distortion, a kind of cascade Mach-Zehnology modulator is disclosed, in order to reduce third order intermodulation distortion in analog communication system.In addition, the paper of being delivered on IEEE periodical QuantumElectronics (Vol.QE-17 No.11, in November, 1981) by people such as Masayuki Izutsu that is entitled as IntegratedOptical SSB Modulator/Frequency Shifter discloses a kind of analog-to-frequency converter that comprises parallel interference modulator of setting up.Use the device of high order function waveguide interferometer all to only limit to simulation application in the prior art.
Freely modulate for chirp, the modulator transition function of high order function waveguide interferometer can be expressed as:
E=[(e
jθ/2+e
-jθ/2)/2]
N=cos
N(θ/2) (1)
Here E represents the complex amplitude of the E field of light, and-representative adds modulation, and N is an exponent number, and light intensity can be expressed as:
I=[(e
jθ/2+e
-jθ/2)/2]
2N=cos
2N(θ/2) (2)
Fig. 2 a illustrates the sketch of Mach-Zehnder interferometer (MZI) 100 when exponent number N=1 in the prior art.Input optical signal 102 is separated into first Waveguide branching 104 and second Waveguide branching 106.Modulation signal 107 inserts input electrode 108.Modulator transition function of the prior art can be expressed as during N=1 shown in Fig. 2 a:
E=[(e
jθ/2+e
-jθ/2)/2]=cos(θ/2) (3)
Owing to do not have chirp or phase shift, transition function is derived cos (θ/2), thereby the imaginary number composition that does not change with θ among the E.
Fig. 2 b illustrates the transition function that inserts modulation signal and output intensity according to Mach-Zehnder interferometer in the prior art shown in Fig. 2 a.The modulation signal of tool sinusoidal frequency is by input electrode 108 modulation Mach-Zehnder interferometers 100, and the output terminal 110 of interferometer produces the output pulse of the cosine wave (CW) transition function combination that comprises sinusoidal wave input signal and interferometer 100.
Fig. 2 c illustrates with the time domain output signal during Mach-Zehnder interferometer 100 in the prior art shown in the sinusoidal signal modulation Fig. 2 a that inserts input electrode 108., promptly corresponding shown in Fig. 2 c with the double scanning of modulator transition function corresponding to the output signal of the modulation signal that surpasses the 2Pi radian.Modulator 100 is biased so that modulation signal is closed and the light intensity maximum.Modulation signal scans the peaked transition function of light intensity.The signal that is produced has the double frequency of modulation signal.
Fig. 3 illustrates the embodiment that comprises the pulse producer 150 of high order function waveguide interferometer according to the present invention.Pulse producer 150 has light intensity to the response of the quadravalence of modulation signal, thereby possesses than the transition function of " sharply " obviously more of Mach-Zehnder interferometer in the prior art shown in Figure 2.Pulse producer 150 comprises a nested structure: exterior part is that a Mach-Zehnder interferometer 154 and inner part are the 2nd Mach-Zehnder interferometer 152, and just second interference modulator is optically coupled to a branch arm of first interference modulator.Inner Mach-Zehnder interferometer 152 comprises a Phi control voltage electrode 156 and is used to insert modulation signal.It is that to be used to insert modulation signal be bias voltage signal to bias electrode 158 that outside Mach-Zehnder interferometer 154 comprises a Theta control voltage electrode.
Among the embodiment, metal electrode is used to provide the device of the static optical phase on the relative minute arm of an inner Mach-Zehnder interferometer 152 of control and outside Mach-Zehnder interferometer 154. Metal electrode 156 and 158 also is used as provides decay with the light on balance each minute arm, thereby the delustring that obtains expecting under no light state has the light that obtains under the light state expecting to export.Electrode can use in conjunction with 50% " y " branch circuit, and it has temperature, wavelength or instantaneous instability minimum and good stable delustring and the power-balance characteristic of tool.
Inner Mach-Zehnder interferometer 152 and outside Mach-Zehnder interferometer 154 all can be formed by the lithium niobate of X cutting or Z cutting, and they also can be speeds match or temperature compensating type interferometer.In addition, these two interferometers can be the narrow-band interference instrument.Use the narrow-band interference instrument useful to the efficient of optimizing pulse producer.
Especially, pulse producer 150 comprises an input waveguide 160, be divided into first waveguide 162 of outside Mach-Zehnder interferometer 154 and the input end 165 that second waveguide, 164, the first waveguides 162 are optically coupled to inner Mach-Zehnder interferometer 152 at first connector 163.First waveguide 162 is divided into inner first waveguide 166 and inner second waveguide 168 at second connector 167.Inner first waveguide 166 and inner second waveguide 168 are made up output waveguide 172 to form inner Mach-Zehnder interferometer 152 again at the 3rd connector 170.The output waveguide 172 and second waveguide 164 are in the output waveguide 175 of the 4th connector 174 combinations to form outside Mach-Zehnder interferometer 154.
In the practical operation, input optical signal is separated into first and second light signals along input waveguide 160 transmission at first connector 163.First and second light signals externally transmit in first waveguide 162 and outside second waveguide 164 respectively.In one embodiment, the light intensity of first and second light signals respectively is about half of input optical signal intensity.
First light signal continues transmission by inner Mach-Zehnder interferometer 152, is divided into the first inner and second interior lights signal at second connector 167.The transmission in inner first waveguide 166 and inner second waveguide 168 respectively of the first and second interior lights signals.The modulation signal of inner Mach-Zehnder interferometer 152 usefulness access Phi control voltage electrode 156 is modulated at least one phase place or the amplitude of the first interior lights signal.Modulation signal can be the ripple of sinusoidal or predetermined waveform.
The first modulated interior lights signal combines the output that forms the internal intervention instrument with the second interior lights signal at the 3rd connector 170, and its light intensity can be from being modulated to nothing.The output of the internal intervention instrument that obtains like this combines to form the output of external intervention instrument at the 4th connector 174 with second light signal.Second optical signals inserts the modulation signal modulation that Theta promptly setovers and controls voltage electrode 158.The output of external intervention instrument is a composite signal, and its light intensity can be from there being the nothing of becoming.
The transition function of pulse generator embodiment can be expressed as by formula (1) during N=2 shown in Figure 3:
E=[(e
jθ/2+e
-jθ/2)/2]
2=cos
2(θ/2)=(1/2)+(1/2)[(e
jθ/2+e
-jθ/2)/2]=(1/2)+(1/2)cos(θ) (4)
Inner Mach-Zehnder interferometer 152 is by _ cos (θ) representative, and the waveguide 164 with bias electrode 158 is represented by constant term.In the present embodiment, the harmonize phase place of waveguide 164 of the phase place of the inner Mach-Zehnder interferometer 152 of bias electrode 158 usefulness.
The output intensity of pulse producer shown in Figure 3 can be described with following formula:
I=E
2=[_+_cos(θ)]
2 (5)
Among the pulse producer embodiment to N=2, the split ratio between outside first waveguide 162 and outside second waveguide 164 is variable, and its light intensity is shown below:
Io2c(φ,F,θ):=[F·cos(θ)+(1-F)·cos(φ)]
2+F
2·sin(θ)
2 (6)
Here F is the split ratio between E1 ' and E2 ', and θ is the phasing degree with respect to the E2 ' branch of inner Mach-Zehnder interferometer output, the phasing degree when Phi is inner Mach-Zehnder interferometer impressed voltage.
In one embodiment, split ratio is 50%.Among another embodiment, split ratio may be selected to be greater than 50%, to produce the second order maximum value of transition function.In the present embodiment, need reduce modulation voltage, increase the width of no light zone.
Fig. 4 illustrates the transition function between narrow-pulse generator access modulation signal shown in Figure 3 and the output intensity.Between the access modulation signal of narrow-pulse generator and output intensity the transition function of redoublining is arranged.On behalf of modulator, A and B territory point be biased to full light or the transition function when unglazed respectively.Correspondingly, inner Mach-Zehnder interferometer 152 and outside Mach-Zehnder interferometer 154 are biased to homophase or out-phase respectively.For producing the good train of impulses of complete symmetry, modulator should be biased on one of these territory points.Be modulated near the of arbitrary these territory points and will produce good asymmetry pulse.And the voltage between this 2 territory point will be the twice that opens or closes inner Mach-Zehnder interferometer 152 required voltages.This voltage this area is expressed as V-pi, and the unit of modulators drives voltage then typically is decided to be V-pi.
Fig. 5 illustrates generator among the pulse producer embodiment of the present invention was biased and had the input of 10GHz sinusoidal modulation signal at light intensity maximal value place time domain output signal.The output signal that obtains like this has the pulsewidth of about 12ps, and repetition rate is about 20GHz.
According to one embodiment of the present of invention, when generator is biased at light intensity maximal value place scan transfer function, thus as shown in Fig. 2 c, output frequency doubles.When input optical signal was symmetrical about the light intensity maximal value, each input signal cycle produced two strength pulse, so the pulsed frequency of light output has doubled with respect to modulation signal.
In the embodiment shown in fig. 3, incoming frequency is 10GHz, doubles then to produce the light time clock frequency of 20GHz.In embodiment illustrated in fig. 5, pulsewidth is easy to division and reorganization, is used for the data transmission of 40Gb/S with the pulse that produces 12.5ps.
According to another embodiment of the invention, narrow-pulse generator comprises that a plurality of inner Mach-Zehnder interferometers form nested structure.In order to reach desired output intensity characteristic, this structure can comprise the inside Mach-Zehnder interferometer of any amount, and formula (1) can be expressed as during such as exponent number N=3:
E=[(e
jθ/2+e
-jθ/2)/2]
3=cos
3(θ/2)=(1/4)[(e
j3θ/2+e
-j3θ/2)/2]+(3/4)[(e
jθ/2+e
-jθ/2)/2]=(1/4)cos(3θ/2)+(3/4)cos(θ/2)(7)
In one embodiment, electrode is used to control first inner Mach-Zehnder interferometer 202, the second inner Mach-Zehnder interferometer 204 and outside Mach-Zehnder interferometer 206 relevant static optical phases of dividing on the arm.Electrode is owing to the light signal load by metal causes that the excessive optical loss of predetermined quantity changes the optical signal magnitude in the waveguide.When touching metal electrode, the light beam afterbody in the waveguide has load.This load does not have dielectric material (being called cushion) Shi Caiyou usually between metal and waveguide edge.
Among the embodiment, Mach- Zehnder interferometer 202 and 204 electrode 240 with 242 and bias electrode 208 be biased with balance respectively or change the relevant minute light component on the arm, thereby under no light state, obtain desired delustring, obtain the output of desired light under the light state having.Electrode in the present embodiment uses in conjunction with 75% " y " branch circuit 210,212 or coupling mechanism, has the delustring and the power-balance characteristic of expectation.
Inner Mach- Zehnder interferometer 202 and 204 and outside Mach-Zehnder interferometer 206 all can form by the lithium niobate of X cutting or Z cutting.They also all can be speeds match or temperature compensating type interferometer.In addition, inner Mach- Zehnder interferometer 202 and 204 and outside Mach-Zehnder interferometer 206 also can be the narrow-band interference instrument.Use the narrow-band interference instrument useful to the efficient of optimizing pulse producer.
Especially, pulse producer 200 comprises input waveguide 214, and it is divided into first waveguide 216 and second waveguide 218 of outside Mach-Zehnder interferometer 206 at first connector 210.Connector 210 is 75% photo-coupler in one embodiment.First waveguide 216 is optically coupled to the first input end 223 of the first inner Mach-Zehnder interferometer 202.First input end 223 is divided into first inner first waveguide 224 and first inner second waveguide 226 at second connector 225.First inner first waveguide 224 and first inner second waveguide 226 reconfigure to form first output waveguide 233 of the first inner Mach-Zehnder interferometer 202 at the 3rd connector 232.
In the practical operation, input optical signal is split into first and second light signals along input waveguide 214 transmission at first connector 210.First and second light signals externally transmit in first waveguide 216 and outside second waveguide 218 respectively.First and second light signals in one embodiment have about 75% split ratio.
First light signal continues transmission by the first inner Mach-Zehnder interferometer 202, is split into the first inner and second interior lights signal at second connector 225.The transmission in first inner first waveguide 224 and first inner second waveguide 226 respectively of the first and second interior lights signals.The modulation signal of first inner its electrode 240 of Mach-Zehnder interferometer 202 usefulness access is modulated at least one phase place or the amplitude of the first interior lights signal.Modulation signal can be the ripple of sinusoidal or predetermined waveform.The first modulated interior lights signal combines the output that forms the first internal intervention instrument with the second interior lights signal at the 3rd connector 232, and its light intensity can be from being modulated to nothing.
Second light signal splits into the third and fourth interior lights signal at the 4th connector 229.The transmission in second inner first waveguide 228 and second inner second waveguide 230 respectively of the third and fourth interior lights signal.The modulation signal of second inner its electrode 242 of Mach-Zehnder interferometer 204 usefulness access is modulated at least one phase place or the amplitude of the 4th interior lights signal.Modulation signal can be the ripple of sinusoidal or predetermined waveform.The 4th modulated interior lights signal combines the output that forms the second internal intervention instrument with the 3rd interior lights signal at the 5th connector 234, and its light intensity can be from being modulated to nothing.
The output of the first and second internal intervention instrument that obtain like this is in the output of the 6th connector 212 combinations with formation external intervention instrument.Second interferes output signal to be access in the modulation signal modulation of biasing control voltage electrode 208.Insert the phase place of two inner Mach-Zehnder interferometers of signal adjustment of bias electrode 208 in one embodiment, eliminated the phase shift of coupling mechanism basically.The bias point of two inner Mach-Zehnder interferometers also can be controlled relatively.The output signal of external intervention instrument is a composite signal, and light intensity can be from there being the nothing of becoming.
Pulse producer when Fig. 7 illustrates according to exponent number N=4 of the present invention.This embodiment can be expressed as with formula (1):
E=[(e
jθ/2+e
-jθ/2)/2]
4=cos
4(θ/2)=(1/8)[(e
j2θ+e
-j2θ)/2]+(1/2)[(e
jθ+e
-jθ)/2]+(3/8)=(1/8)cos(2θ)+(1/2)cos(θ)+(3/8)(8)
Among the embodiment, electrode is used to control first inner Mach-Zehnder interferometer 280, second inner Mach-Zehnder interferometer the 282, the 3rd inner Mach-Zehnder interferometer 274 and outside Mach-Zehnder interferometer 300 relevant static optical phases of dividing on the arm.Mach- Zehnder interferometer 280 and 282 electrode and two bias electrodes 276 with 292 also in order to balance or change the relevant light component that divides on the arm, thereby under no light state, obtain desired delustring, obtain desired light under the light state and export having.Electrode in the present embodiment uses in conjunction with 75% " y " branch circuit 258,298 or coupling mechanism, has the delustring and the power-balance characteristic of expectation.
First inner Mach-Zehnder interferometer 280, second inner Mach-Zehnder interferometer the 282, the 3rd inner Mach-Zehnder interferometer 274 and outside Mach-Zehnder interferometer 300 all can be formed by the lithium niobate of X cutting or Z cutting.They also all can be speeds match or temperature compensating type interferometer.Mach-Zehnder interferometer 280,282 and 274 also can be the narrow-band interference instrument.Use the narrow-band interference instrument useful to the efficient of optimizing pulse producer.
Especially, pulse producer 250 comprises input waveguide 252, and it is divided into first waveguide 254 and second waveguide 256 of outside Mach-Zehnder interferometer 300 at first connector 255.Connector 255 is the balanced type photo-coupler in one embodiment.First waveguide 254 is optically coupled to second connector 258.Second connector is 75% " y " branch circuit in one embodiment.Second connector 258 comprises an input end of receiving the 3rd inner Mach-Zehnder interferometer 274.
In the practical operation, input optical signal splits into first and second light signals along input waveguide 252 transmission at first connector 255.First and second light signals externally transmit in first waveguide 254 and outside second waveguide 256 respectively.The light intensity of first and second light signals respectively is about half of input optical signal intensity in one embodiment.
First light signal by connector 258 transmission splits into the first inner and second interior lights signal.The second interior lights signal that transfers to the 3rd connector 267 splits into the third and fourth interior lights signal.The transmission in first inner second waveguide 266 and first inner first waveguide 268 respectively of the third and fourth interior lights signal.The modulation signal of first inner its electrode 281 of Mach-Zehnder interferometer 280 usefulness access is modulated at least one phase place or the amplitude of the 3rd interior lights signal.Modulation signal can be the ripple of sinusoidal or predetermined waveform.The 3rd modulated interior lights signal and the 4th interior lights signal combine the output that forms the first internal intervention instrument at the 4th connector 270, and it can be by from being modulated to nothing.The first interior lights signal combines the output signal that forms the 3rd internal intervention instrument by 260 transmission of second inner waveguide with the output of the first internal intervention instrument at the 5th connector 298.The output signal of the 3rd internal intervention instrument is access in the modulation signal modulation of bias electrode 276.The output signal of the 3rd internal intervention instrument is optically coupled to the output signal that the first outside output waveguide 278 forms the first external intervention instrument by the 5th connector 298, and it can be by from being modulated to nothing.
Second light signal transfers to the input end 284 of the second inner Mach-Zehnder interferometer 282 by outside second waveguide 256, at last to the 6th connector 287.The 6th connector 287 splits into the 5th and the 6th interior lights signal with second light signal.The transmission in second inner second waveguide 286 and second inner first waveguide 288 respectively of the 5th and the 6th interior lights signal.The modulation signal of second inner its electrode 283 of Mach-Zehnder interferometer 282 usefulness access is modulated at least one phase place or the amplitude of the 5th interior lights signal.Modulation signal can be the ripple of sinusoidal or predetermined waveform.The 5th modulated interior lights signal forms the output signal of the second external intervention instrument in the 7th connector 290 and the 6th interior lights signal combination, and it can be by from being modulated to nothing.
The output signal of the first and second external intervention instrument that obtain like this is in the output signal of the 8th connector 296 in conjunction with formation external intervention instrument.The output signal of the second external intervention instrument is access in the modulation signal modulation of biasing control voltage electrode 292.The phase place of the bias electrode 292 inner Mach-Zehnder interferometers of adjustment and second inner waveguide 260 is to eliminate the phase shift of coupling mechanism.The bias point of inner Mach-Zehnder interferometer also can be controlled relatively.The output signal of external intervention instrument is a composite signal, and light intensity can be from there being the nothing of becoming.
Fig. 8 illustrates the pulse producer with the nested interference modulator of N.Square frame 352 and 354 is represented the combination or the Distributed Power Architecture of " y " branch circuit and coupling mechanism, to obtain the split ratio of each desired branch.There is a large amount of Passive Power flow dividing structures in the prior art, such as using multiple-mode interfence (MMI) structure, perhaps such average body (even bulk) the luminous power part flow arrangement of lens combination.
Mach-Zehnder interferometer 356,360 and 364 is modulated at the multiple light signal of transmission in the pulse producer 350.Bias electrode 358,362 and 366 phase places of harmonizing nested modulator each minute arm.Exponent number for given, be not _ all multiples of/2 all manifest the driving stage in the structure.For example exponent number N=3 comprise modulating stage 3_/2 and _/2, and exponent number N=4 comprise modulating stage 2_ and _.In addition, constant term represent passive wave guide divide arm only for even-order (be N=2,4 ...).
According to another discovery of the present invention, can obtain more high-order transition function with two of cascades or the more nested modulator of low order.The quantity of the nested modulator of cascade can be decided by the complexity (typically using the feedback loop ACTIVE CONTROL) of the modulation signal quantity that inserts, required modulate intensity and biasing control.Such as the modulator on two N=2 rank of cascade obtains and a transition function that the N=4 modulator is identical, and the two all needs two modulation signals.But the modulator of four N=1 of cascade is not-so-practical to obtain identical function, because need to insert four rather than two synchronous modulation signals.
Fig. 9 illustrates the cascade structure according to the nested modulator 456 of two exponent number N=2 of the present invention.This structure has the transition function identical with the modulator of an exponent number N=4.Modulator 150 comprises nested inside Mach-Zehnder interferometer 152 and outside Mach-Zehnder interferometer 154.Outside Mach-Zehnder interferometer 154 has an input waveguide 160 and an output waveguide 175.Output waveguide 175 is optically coupled to the input waveguide 160 ' of second modulator 150 '.Except that the input waveguide 160 ' of modulator 150 ' receives the output light signal of modulator 150 but not the external optical signal, modulator 150 ' is identical with modulator 150 on 26S Proteasome Structure and Function.
In the practical operation, input optical signal is along input waveguide 160 transmission of Mach-Zehnder interferometer 150, and after 163 shuntings of first connector, signal reconfigures at the 4th connector 174 by 150 transmission of Mach-Zehnder interferometer.Signal after the combination enters the input waveguide 160 ' of modulator 150 ' at this, runs into the 5th connector 163 '.After the 163 ' shunting of the 5th connector, signal passes through MZI150 ' transmission and reconfigures at the 8th connector 174 '.The output signal that obtains like this is corresponding to the modulator output of exponent number N=4.
According to one embodiment of the present of invention, modulator is by linear frequency modulation, the modulation signal frequency displacement that is access in of light signal just.The transition function of linear frequency modulation operation comprises the item of plural composition, and it represents modulation phase shift.Be expressed as in conjunction with formula (1) complex item:
E=[(e
jθ/2+e
-jθ/2)/2]
N?e
mθ=cos
N(θ/2)e
mθ(9)
Here the value of m depends on required chirp intensity.
Figure 10 illustrates the embodiment of the chirp generator 370 of exponent number N=4.The linear frequency modulation generator comprises the phase-modulator 372 that is positioned outside Mach-Zehnder interferometer 300 output terminals.The characteristic of chirp is by the modulation signal decision of the electrode 374 that inserts phase-modulator 372.
Figure 11 illustrates the chirp generator 380 of exponent number N=4.The phase-modulator 382,386 and 390 on being added to waveguide 260 ', 272 ' and 294 ' respectively, structural similarity shown in Figure 11 and embodiment illustrated in fig. 7.The chirp characteristic is by the modulation signal decision that inserts electrode 384,388 and 392.Phase-modulator 382,386 and 390 in one embodiment can make the amount of phase modulation on each minute arm equate.
Figure 12 illustrates according to the present invention and uses unbalanced type to recommend the pulse producer of design in inner Mach-Zehnder interferometer.This design synthesis phase modulation (PM) and amplitude-modulated function.The phase-modulator 382 on being added to waveguide 260 ', structure shown in Figure 12 is to shown in Figure 7 similar.
Because the relation of required fixed number in cos (), Mach-Zehnder interferometer 280 must use the driving that doubles Mach-Zehnder interferometer 282, so the degree of asymmetry of two inner Mach- Zehnder interferometers 280 and 282 is inequality.So the waveguide of Mach-Zehnder interferometer 280 divides arm also must use the modulation that doubles Mach-Zehnder interferometer 282.But must mate because the net phase of Mach- Zehnder interferometer 280 and 282 output terminals is moved, for compensating double drive level, Mach-Zehnder interferometer 280 should have less degree of asymmetry.An advantage of present embodiment is that all modulated structures are parallel connection, and the size of phase-modulator electrode is limited, so reduced the space of occupying of device.
Figure 13 illustrates a N rank chirp generator.As shown, phase modulation (PM) and bias capability are incorporated into electrode 422,424 and 426.Perhaps, phase modulation (PM) can be the electrode that separates with bias electrode.Among another embodiment, use asymmetric electrode that phase modulation (PM) is comprehensively advanced inner Mach-Zehnder interferometer.
Pulse producer according to the present invention is specially adapted to produce narrow Digital Logic " RZ " pulse.Pulse producer of the present invention also is specially adapted to produce the signal with anticipant output character flex point, makes the output transition function have broad no-output light intensity zone with respect to control signal.Such signal has strengthened the having of output/no light state and has helped producing having/no delustring of optimization.
Narrow-pulse generator of the present invention can be further appreciated by the operation of embodiment.Narrow-pulse generator of the present invention can transmit the 40Gb/s data, an available 40Gb/s system architecture or two 20Gb/s systems.Pulse producer is used for light time territory multiplexing (OTDM) system architecture in one embodiment.
Figure 14 illustrates the function of extinction ratio and pulsewidth and RMS power in the one embodiment of the invention.As shown, can produce with 50ps (20Gb/s recurrence interval) with nested Mach-Zehnder device embodiment is 12ps wide (40Gb/s pulsewidth) stream of pulses at interval.This needs frequency of utilization is that 10GHz and four times of V-pi voltages are modulated near the ON state (A point among Fig. 4) of modulator biasing and finished.Figure 14 shows the extinction ratio 450 of one embodiment of the present of invention and pulsewidth 452 function about the RF driving power.When pulsewidth is about 12ps (24% pulse repetition time was 12ps/50ps), when driving voltage was four times of V-pi (30dBm), extinction ratio 450 was a maximal value.Present embodiment needs the driving voltage of four times of V-pi so that eliminate all signals at the OFF state.Signal non-zero when the driving voltage deficiency will cause modulator OFF state, and pulse is broadened, but can not influence the peak light pulse power.
Figure 15 a and Figure 15 b illustrate by+30dBm and+two 20Gb/s pulse producers of 27dBm power drive.In one embodiment, nested modulator structure needs inside and external modulator to be biased to the ON state with Optimizing operation.The biasing of internal intervention instrument refers to symmetry biasing sometimes, and it has influence on the interval of adjacent pulse, shown in Figure 16 a during symmetrical bias offset 0.2V-pi.The biasing of external intervention instrument has influence on the extinction ratio of pulse producer, and it often is called as extinction ratio (ER) biasing.Light output when Figure 16 b illustrates modulator band ER bias offset.It is the function of the ER bias voltage of unit with V-pi that Figure 16 c illustrates the extinction ratio conduct.In one embodiment, when being biased in the ON state, inside and outside Mach-Zehnder interferometer obtains just bias thereby can obtain biasing control.
Two 20Gb/s pulse producers can be the stream of pulses that the modulation of 20GHz signal produces a 40Gb/s by means of the biasing of (the B point among Fig. 4) under the OFF state and with frequency.Under this mode, reduce driving power and can cause increasing the optical loss of equipment and reduce light impulse length, and extinction ratio remains the function with respect to driving power.Four times of V-pi driving powers of an embodiment of pulse producer are 33.6dBm under the 20GHz driving frequency, and are higher relatively.But the action need modulator of the equipment of a common 40Gb/s pulse mode is with modulated less than the voltage of four times of V-pi.
Figure 17 illustrates the pulsewidth 460 of a 40Gb/s pulse producer in the one embodiment of the invention and the function between additional light loss 462 and driving power.Can obtain the pulse of 12ps during for+31.75dBm at driving power, the offset under this driving power is 0.8dB.Correspondingly, the pulsewidth of driving power during for+27.5dBm is 10.1ps, and luminous power is compensated for as 6.0dB.Figure 18 a and Figure 18 b illustrate respectively power input for+31.75dBm and+light output during 27.5dBm.
The present invention uses nested modulator structure as the advantage of a 40Gb/s pulse producer to be, does not need the sacrificial light capacity that the extremely short pulse of pulsewidth about 11ps-13ps just can be provided.The loss of one embodiment of the present of invention additional light is less than 2dB.
Pulse producer of the present invention can comprise the interference modulator with corrective network, as U.S. Patent Application Serial Number 09/309444 described " using the exterior light modulation of non-colinear type corrective network ", this invention is common for the application's assignee, is hereby incorporated by reference.Corrective network is in connector place and electric waveguide electric coupling, along and the non-colinear second transmission direction transmission of electric signals of first transmission direction.In one embodiment, corrective network comprises in fully energized network, inductor-capacitor " Pi " network, row ripple coupling mechanism, wave filter and the line transformer one at least.
Corrective network at least will be at the connector place respectively with respect to the phase place of light signal or the phase place or the amplitude of amplitude correc-tion electric signal, and the electric signal that will revise returns to electric waveguide again.Corrective network can be time delay or phase-delay network.
The benefit of using compensation network is that the electrical loss of per unit can be starkly lower than the loss of per unit length electric waveguide so that minimize the RF loss among the present invention.Another benefit of corrective network is that it can removably mate electro-optic device, thereby can be replaced by other corrective network.Another benefit is that the temperature dependency of corrective network can be inversely proportional to the temperature dependency of electrooptical material, thereby compensates the nonlinear temperature of electrooptical material.
Among the embodiment, corrective network is a phase-delay network, and it revises the phase place of electric signal, so that the phase differential between connector place electric signal and light signal is reduced with respect to the phase differential of the modulation on optical waveguide input electric signal and the light signal or is zero substantially.Among another embodiment, corrective network is a phase-delay network, and with respect to the phase place of light signal phase modulation correction electric signal, this predetermined delay is variable in 0 to 180 degree scope at the connector place for its use predetermined delay.The phase place of connector place electric signal can be corrected for 180 degree basically with respect to the light signal phase modulation in the present embodiment.
In the practical operation, each in a plurality of corrective networks all use predetermined phase delay respectively on the connector separately in a plurality of connectors with respect to the phase place of the phase modulation correction electric signal on the light signal, and the electric signal that will revise returns to electric waveguide.Predetermined delay in 0 to 180 degree scope variable and in one embodiment this delay be essentially 180 the degree.Among another embodiment, each corrective network respectively with respect to the phase modulation correction on connector place light signal separately in the phase place of junction electric signal separately so that the electric signal at each connector place basically with light signal on the modulation homophase.
The present invention is specifically described with reference to above-mentioned illustrating with described embodiment; those of ordinary skills are readily appreciated that; the present invention all belongs to the claimed scope of claims in the variation that also can have under the situation that does not break away from its spirit on various ways and the details.
Claims (24)
1. optical pulse generator with high-order transition function, this generator comprises:
A) first interference modulator contains a light input end, an electrical input, first fen arm, second fen arm and a light output end;
B) second interference modulator contains a light input end, an electrical input, first fen arm, second fen arm and a light output end, and second interference modulator is optically coupled to second fen arm of first interference modulator,
Wherein the light output end of first interference modulator produces pulse with the repetition rate that is proportional to electric signal frequency multiple, this electric signal inserts at least one electrical input of first and second interference modulators, and duty of ratio is inversely proportional to the exponent number of the transition function of optical pulse generator.
2. optical pulse generator as claimed in claim 1 further comprises:
A) the 3rd interference modulator, its input end is optically coupled to the output terminal of first interference modulator, and it also comprises first fen arm, second fen arm and electrical input;
B) the 4th interference modulator contains first, second minute arm and electrical input, and it is optically coupled to second fen arm of the 3rd interference modulator;
Wherein the light output end of the 3rd interference modulator produces pulse with the repetition rate that is proportional to electric signal frequency multiple, this electric signal inserts at least one electrical input of the second and the 4th interference modulator, and duty of ratio is inversely proportional to the exponent number of the transition function of optical pulse generator.
3. optical pulse generator as claimed in claim 1, the wherein phase place of at least one modulating light pulse in first and second interference modulator.
4. optical pulse generator as claimed in claim 1, the wherein amplitude of at least one modulating light pulse in first and second interference modulator.
5. optical pulse generator as claimed in claim 1, wherein at least one in first and second interference modulator comprises a Mach-Zehnder modulator.
6. optical pulse generator as claimed in claim 1 forms wherein that the substrate of at least one comprises lithium niobate substrate in first and second interference modulator.
7. optical pulse generator as claimed in claim 6, wherein lithium niobate substrate is the X cutting.
8. optical pulse generator as claimed in claim 6, wherein lithium niobate substrate is the Z cutting.
9. optical pulse generator as claimed in claim 1, wherein at least one in first and second interference modulator is speeds match haply.
10. optical pulse generator as claimed in claim 1, wherein in first and second interference modulator at least one is temperature compensation haply.
11. optical pulse generator as claimed in claim 1, wherein at least one in first and second interference modulator has the bandwidth that is limited to bandwidth basically, to increase the efficient of light signal modulation.
12. optical pulse generator as claimed in claim 1, wherein in first and second interference modulator the split ratio between the first and second fens arms of at least one roughly less than 1.
13. optical pulse generator as claimed in claim 1 further comprises a phase-modulator, it is coupled in series to the output terminal of first interference modulator, the phase-modulator modulation signal linear frequency modulation light pulse that inserts its electrical input.
14. the optical pulse generator with high-order transition function, this generator comprises:
A) interference modulator that connects of a plurality of parallel opticals, each modulator contain first, second a minute arm and electrical input,
Wherein the light output end of pulse producer produces the light pulse with the repetition rate that is proportional to electric signal frequency multiple, this electric signal inserts in a plurality of interference modulators the electrical input of at least one, and duty of ratio is inversely proportional to the exponent number of the transition function of optical pulse generator.
15. optical pulse generator as claimed in claim 14, further comprise a bias electrode, be electrically coupled in a plurality of interference modulators the output terminal of at least one, wherein insert the phase place of the voltage correction of bias electrode from the light signal of at least one in a plurality of interference modulators.
16. optical pulse generator as claimed in claim 14 further comprises a phase-modulator, is coupled in a plurality of interference modulators the output terminal of at least one, phase-modulator is introduced chirp.
17. optical pulse generator as claimed in claim 14 further comprises a phase-modulator, is coupled to the light output end of optical pulse generator, phase-modulator is introduced chirp.
18. the method with the nested interference modulator generation light pulse of high-order, this method comprises:
A) receive input beam;
B) input beam is divided into first and second light beam;
C) the electric light biasing transmits the material of first light beam, makes the characteristic changing of first light beam;
D) second light beam is divided into the 3rd and the 4th light beam;
E) material of at least one in electric light biasing transmission the 3rd and the 4th light beam is so that the characteristic changing of at least one in the 3rd and the 4th light beam;
F) modulate in the 3rd and the 4th light beam at least one with electric signal; With
G) interfere the first, the 3rd and the 4th light beam to produce light pulse, the repetition rate of light pulse is proportional to the frequency multiple of electrical modulation signal, and its dutycycle is inversely proportional to the exponent number of nested interference modulator.
19. method as claimed in claim 18, wherein the step of the material of electric light biasing transmission first light beam comprises corrects bias voltage, so that light pulse has predetermined extinction ratio.
20. method as claimed in claim 18 further comprises at least one the split ratio of proofreading and correct the input beam and second light beam, makes light pulse have predetermined extinction ratio.
21. method as claimed in claim 18, wherein electric signal comprises sine wave signal.
22. method as claimed in claim 18, wherein electric signal comprises and has in modulation the 3rd and the 4th light beam at least one waveform so that light pulse comprises the signal of orphan's waveform.
23. method as claimed in claim 18 is wherein modulated the electric signal of at least one in the 3rd and the 4th light beam and is comprised signal about light intensity maximal value symmetry.
24. a method that produces return-to-zero pulse, this method comprises:
A) receive input beam;
B) input beam is divided into first and second light beam;
C) the electric light biasing transmits the material of first light beam, makes the characteristic changing of first light beam;
D) second light signal is divided into the 3rd and the 4th light beam;
E) material of at least one in electric light biasing transmission the 3rd and the 4th light beam is so that the characteristic changing of at least one in the 3rd and the 4th light beam;
F) modulate in the 3rd and the 4th light beam at least one with electric signal; And
G) interfere the first, the 3rd and the 4th light beam to produce return-to-zero pulse, this pulsed frequency is the multiple of electrical modulation signal frequency.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US13619699P | 1999-05-25 | 1999-05-25 | |
| US60/136,196 | 1999-05-25 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN1315013A true CN1315013A (en) | 2001-09-26 |
Family
ID=22471775
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 00801155 Pending CN1315013A (en) | 1999-05-25 | 2000-05-23 | Optical pulse generation using a high order function waveguide interferometer |
Country Status (3)
| Country | Link |
|---|---|
| CN (1) | CN1315013A (en) |
| AU (1) | AU7469300A (en) |
| CA (1) | CA2336790C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102215069A (en) * | 2011-05-26 | 2011-10-12 | 北京交通大学 | Frequency-adjustable triangle-wave photon generator |
| CN102412904A (en) * | 2011-11-10 | 2012-04-11 | 北京交通大学 | Triangular optical pulse generating device based on double-electrode Zehnder modulator |
-
2000
- 2000-05-23 CN CN 00801155 patent/CN1315013A/en active Pending
- 2000-05-23 CA CA002336790A patent/CA2336790C/en not_active Expired - Fee Related
- 2000-05-23 AU AU74693/00A patent/AU7469300A/en not_active Abandoned
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102215069A (en) * | 2011-05-26 | 2011-10-12 | 北京交通大学 | Frequency-adjustable triangle-wave photon generator |
| CN102412904A (en) * | 2011-11-10 | 2012-04-11 | 北京交通大学 | Triangular optical pulse generating device based on double-electrode Zehnder modulator |
| CN102412904B (en) * | 2011-11-10 | 2014-05-28 | 北京交通大学 | Triangular optical pulse generating device based on double-electrode Zehnder modulator |
Also Published As
| Publication number | Publication date |
|---|---|
| AU7469300A (en) | 2000-12-18 |
| CA2336790C (en) | 2007-01-02 |
| CA2336790A1 (en) | 2000-12-07 |
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