JPH09233031A - Optical multiplex transmission system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To multiplex massive information sets within a prescribed wavelength length without taking a wavelength stability of a light source and a characteristic of an optical filter into account and to send an analog signal with a frequency of 100GHz or over or a digital signal whose bit rate is 100Gbit or more over a long range. SOLUTION: An optical transmission section 2 up-converts plural base band signals into plural high frequency signals whose occupied frequency bands are not overlapped and the high frequency signals are converted into plural optical signals, and they are multiplexed into one optical signal. An optical reception section 4 converts the optical signal into an electric signal being a frequency multiplex signal, it is subject to frequency heterodyne detection to recover plural base band signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical combining transmission system for transmitting information by a plurality of lights, and more particularly to an optical combining transmission for performing optical transmission using an optical transmitter and an optical receiver that do not use an optical demultiplexer. Regarding the system.

[0002]

2. Description of the Related Art Conventionally, an optical combining transmission system for transmitting information using optical signals having different wavelengths has been proposed as shown in FIG. 4 (example: NTT "broadband dedicated optical transmission system"). , Nikkei Technical Book Co., Ltd., Optical fiber application technology compilation, 1986, 12.1.
0, P539 to P540). The optical combining transmission system 101 shown in FIG. 4 has a baseband occupied frequency band Δf _{1 to} Δf.
The _N baseband signals (DC level signals), which are represented by f _N and contain the information to be transmitted, have different wavelengths λ.
After being converted into optical signals of _{1 to} λ _N , these optical signals are optically combined to generate one optical signal (wavelength multiplexed optical signal); The optical transmission line 103 for transmitting the optical signal and the optical signal supplied via the optical transmission line 103 are demultiplexed for each wavelength λ _{1 to} λ _N , and each wavelength λ _{1 to} λ _N And an optical receiving unit 104 for converting each optical signal into N baseband signals including information represented by baseband occupied frequency bands Δf _{1 to} Δf _N.
N represented by f _{1 to} Δf _N and including information to be transmitted
When the individual baseband signals are input, the optical transmitter 10
2 converts each of these baseband signals into optical signals of different wavelengths λ _{1 to} λ _N , and multiplexes them into one optical signal, and then, through the optical transmission line 103, an optical receiving unit. To 104. Then, the optical signal supplied by the optical receiver 104 via the optical transmission path 103 is demultiplexed into wavelengths λ _{1 to} λ _N into a plurality of optical signals, and then these optical signals are electrically converted. Signal (baseband signal) is converted to a baseband occupied frequency band Δf ₁
Output _N baseband signals including information represented by Δf _N.

The optical transmitter 102 is represented by baseband occupied frequency bands Δf _{1 to} Δf _N , and when N baseband signals including information to be transmitted are input, wavelengths λ _{1 to} λ different from each other. First to _Nth optical signals converted into _N optical signals
Electric / optical converters 105a to 105n and N output from the first to Nth electric / optical converters 105a to 105n
Optical multiplexer 1 that photosynthesizes individual optical signals into one optical signal
06, and the baseband occupied frequency band Δf
When _N baseband signals represented by _{1 to} Δf _N and including information to be transmitted are input, the respective baseband signals are converted into optical signals of different wavelengths λ _{1 to} λ _N. At the same time, these optical signals are optically multiplexed and then transmitted to the optical receiving unit 104 via the optical transmission line 103. The optical receiving section 104 includes an optical demultiplexer 107 for demultiplexing the optical signal supplied via the transmission path 103 into optical signals of preset wavelengths λ _{1 to} λ _N , and the optical demultiplexer 107. 10
Converting each optical signal output from the optical signal No. 7 into an electrical signal to generate N baseband signals represented by the occupied baseband frequency bands Δf _{1 to} Δf _N including the information transmitted from the optical transmitter 102. 1st to Nth optical / electrical converter 108a
To 108n, the optical signal supplied via the optical transmission line 103 is demultiplexed into wavelengths λ _{1 to} λ _N to form a plurality of optical signals, and then each of these optical signals is used as a base. The information transmitted from the optical transmission unit 102 side is reproduced by converting into an electric signal (base band signal) of the band occupied frequency band Δf _{1 to} Δf _N.

However, the above-mentioned conventional photosynthetic transmission system 101 has the following problems. That is, such an optical combining transmission system 101
Then, in order to realize large-capacity transmission, first to third laser diode light sources having different wavelengths are used.
The N-th electrical / optical converters 105a to 105n, and the optical combiner 106 and the optical demultiplexer 107 each including an optical filter whose wavelength perfectly matches the wavelength of each laser diode light source are required. However, in such laser diode light sources and optical filters, the wavelength of the laser light emitted from each laser diode light source and the wavelength of the optical signal that can be combined and demultiplexed by the optical filter are Since the wavelength is determined by the physical structure of the filter, it is difficult to increase the number of wavelengths, and there is a problem in that it is considerably difficult to actually realize the photosynthetic transmission system 101 having such a configuration. Further, in such a laser diode light source, when the ambient temperature changes, the wavelength of the optical signal emitted from the laser diode light source greatly changes, so that the first to Nth electrical / optical converters 105a to 10c.
The wavelength interval of the optical signal emitted from 5n or the like has to be set large, which limits the number of optical signals that can be multiplexed within a certain wavelength range.
There is a problem that it is difficult to multiplex a lot of information.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in claim 1, the wavelength stability is fixed within a certain wavelength range without considering the wavelength stability of the light source and the characteristics of the optical filter. An object of the present invention is to provide a photosynthetic transmission system capable of multiplexing a large amount of information and capable of transmitting an analog signal having a frequency of 100 GHz or higher or a digital signal having a bit rate of 100 Gbit or higher for a long distance. Further, in claim 2,
It is an object of the present invention to provide an optical combining transmission system capable of significantly increasing the transmission distance between an optical transmitting section and an optical receiving section.

[0006]

In order to achieve the above-mentioned object, the photosynthetic transmission system according to the present invention is, in claim 1, characterized in that a plurality of inputted baseband signals are up-converted and high frequency signals having different frequencies from each other. After converting each of these high-frequency signals to electrical / optical, a plurality of optical signals are generated, and these optical signals are optically multiplexed, and one optical signal is emitted, and this optical transmission The optical signal emitted from the optical fiber is taken in and transmitted, and the optical signal transmitted by this optical transmission line is converted into a frequency multiplexed signal by optical / electrical conversion, and this frequency multiplexed signal is converted into an optical heterodyne. An optical receiving unit for detecting and reproducing a plurality of baseband signals is provided. A second aspect of the present invention is characterized in that, in the optical combining transmission system according to the first aspect, an optical fiber amplifier is arranged in the middle of the optical transmission line.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. FIG. 1 is a block diagram showing an example of the form of an optical combining transmission system according to the present invention. Photosynthesis transmission system 1 shown in this figure, N-number of the baseband signal frequency of each different frequencies F ₁ to F _N (baseband frequency band occupied Δf ₁ ~Δf _N DC level signal) containing information to be transmitted target An optical transmitter 2 that up-converts the signals and then converts them into optical signals having the same wavelength, and optically multiplexes these optical signals to generate one optical signal.
And an optical fiber cable or the like, which transmits an optical signal output from the optical transmitter 2, and an optical signal supplied through the optical transmission line 3 after being converted into an electric signal, An optical receiver 4 for performing frequency heterodyne detection on the signal to generate _N baseband signals (DC level signals having occupied baseband frequency bands Δf _{1 to} Δf _N ), and N including information to be transmitted. When a plurality of baseband signals are input, the optical transmitter 2 up-converts each of these baseband signals to convert them into high-frequency signals of different frequencies, and converts each of these high-frequency signals into light of the same wavelength. After being converted into a signal, these optical signals are optically multiplexed into one optical signal, which is transmitted to the optical receiving unit 4 via the optical transmission line 3.
Then, after converting the optical signal supplied through the optical transmission line 3 by the optical receiving unit 4 into an electric signal, the electric signal is subjected to frequency heterodyne detection to obtain N baseband signals including information from the transmission source. It reproduces the signals and outputs them.

As shown in FIG. 2, the optical transmitter 2 includes first to Nth frequency up-converting oscillators 5a to 5n which generate high-frequency signals of preset frequencies F _{1 to} F _N , respectively.
If, when the N baseband signal containing information to be transmitted object (DC level signal of the baseband frequency band occupied Δf ₁ ~Δf _N) is input, each of these baseband signal and the first to N First to N-th mixers 6a to 6n for respectively mixing the high frequency signals output from the frequency up-conversion oscillators 5a to 5n with each other to convert the high frequency signals to the high frequency signals of the frequencies F ₁ + Δf _{1 to} F _N + Δf _N , A wide band star and first to Nth electrical / optical converters 7a to 7n for respectively converting the high frequency signals output from the first to Nth mixers 6a to 6n into preset optical signals of the same wavelength. An optical multiplexer 8 configured by an optical coupler or the like, which optically multiplexes the optical signals output from the first to Nth electrical / optical converters 7a to 7n to generate one optical signal. . When N baseband signals including information to be transmitted are input, these baseband signals are up-converted by using high frequency signals having frequencies F _{1 to} F _N different from each other to obtain a frequency F ₁ + Δf _{1 to} F _N + Δ
After converting each of the high frequency signals of f _N to each of the high frequency signals to generate an optical signal having the same wavelength, N optical signals are generated. The signal is converted into a signal and transmitted to the optical receiver 4 via the optical transmission line 3.

The optical receiver 4 has an optical transmission line 3 as shown in FIG.
An optical / electrical converter 9 for converting an optical signal supplied via the optical signal into an electric signal (frequency multiplexed signal) and a _first local oscillation signal for generating a local oscillation signal having a preset frequency F _{1 to} F _N.
-Nth frequency down-converting oscillators 10a to 10n
And each of the local oscillation signals output from the first to Nth frequency down-converting oscillators 10a to 10n and the frequency-multiplexed signal output from the optical / electrical converter 9, respectively, to perform frequency heterodyne detection. At the same time, bandpass filtering is performed to extract a signal having a preset frequency, and N baseband signals (baseband occupied frequency band Δf ₁
And a first to N input signal band selection filter with mixer 11a~11n reproducing the DC level signal) of ～Derutaf _N. When an optical signal is supplied through the optical transmission line 3, the optical signal is converted into an electric signal to generate a frequency-multiplexed signal, and then a frequency using local oscillation signals of different frequencies F _{1 to} F _N is used. Each of the frequency-multiplexed signals is down-converted by the heterodyne detection process, and N baseband signals including information obtained from the transmission source are output.

At this time, as the optical / electrical converter 9, at present,
Since a device for converting an optical signal up to about 150 GHz into an electric signal has been developed, an analog signal having a frequency of 100 GHz or more or a digital signal having a bit rate of 100 Gbit or more can be transmitted over a long distance. As described above, in this embodiment, the optical transmitter 2 side up-converts a plurality of baseband signals into a plurality of high-frequency signals that do not overlap in occupied frequency bands, and then converts the respective high-frequency signals. A plurality of optical signals obtained by converting them into optical signals are optically multiplexed and transmitted by one transmission path, and the optical signals are converted into electrical signals at the optical receiving section 4 side to be frequency multiplexed signals. Since the frequency heterodyne detection is performed to reproduce a plurality of baseband signals,
An analog signal having a frequency of 100 GHz or higher or a digital signal having a bit rate of 100 Gbit or higher can be transmitted over a long distance without considering the wavelength stability of the light source and the characteristics of the optical filter. Further, in the above-described embodiment, the wavelengths of the laser diode light sources used in the first to Nth electrical / optical converters 7a to 7n are set to the same wavelength. Converter 7
The wavelengths of the laser diode light sources used in a to 7n may be different from each other by a predetermined number.

Also in this manner, the optical receiving section 4 demultiplexes the optical signal for each wavelength, and then frequency heterodyne detection is performed for each wavelength to regenerate a plurality of baseband signals. However, a large amount of information can be transmitted from the optical transmitter 2 to the optical receiver 3 by optically multiplexing a larger number of optical signals. Further, in the above-described embodiment, the generally used optical fiber cable is used as the optical transmission line 3. However, instead of such an optical fiber, an optical fiber amplifier is provided on the way. An optical fiber cable may be used. At this time, by matching the wavelength of the optical signal emitted from the laser diode light source provided in the optical transmitter 2 with the wavelength of the optical signal at which the amplification characteristic of the optical fiber amplifier is maximized, the length of the optical transmission line is reduced. The transmission distance between the optical transmission unit 2 and the optical reception unit 4 can be significantly increased by greatly increasing the length.

[0012]

As described above, according to the present invention, in claim 1, a plurality of high frequency waves are provided so that the optical transmitter section up-converts a plurality of baseband signals so that the occupied frequency bands do not overlap each other. After converting each high-frequency signal into an optical signal, the optical signals obtained by converting each high-frequency signal into an optical signal are optical-multiplexed into one optical signal, which is transmitted, and the optical signal is electrically converted by the optical receiving unit side. After converting to a signal and making it a frequency-multiplexed signal, by performing frequency heterodyne detection and reproducing multiple baseband signals, a fixed wavelength range can be obtained without considering the wavelength stability of the light source and the characteristics of the optical filter. A lot of information can be multiplexed and
Analog signal with a frequency of GHz or higher or 100G
A digital signal having a bit rate equal to or higher than bit can be transmitted over a long distance. Further, according to claim 2, an optical fiber amplifier is arranged in the middle of the optical transmission line, and the wavelength of the optical signal emitted from the optical transmission unit side is matched with the amplification characteristic of the optical fiber amplifier, whereby The transmission distance to the optical receiver can be significantly increased.

[Brief description of drawings]

FIG. 1 is a block diagram showing an example of an embodiment of an optical combining transmission system according to the present invention.

FIG. 2 is a block diagram showing a detailed circuit configuration example of an optical transmission section shown in FIG.

FIG. 3 is a block diagram showing a detailed circuit configuration example of an optical receiving unit shown in FIG.

FIG. 4 is a block diagram showing an example of a conventionally known photosynthetic transmission system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical combining transmission system 2 Optical transmission part 3 Optical transmission line 4 Optical receiving part 5a-5n 1st-Nth frequency up-conversion oscillators 6a-6n 1st-Nth mixer 7a-7n 1st-Nth electrical / optical Converter 8 Optical multiplexer 9 Optical / electrical converter 10a to 10n 1st to Nth frequency down-conversion oscillators 11a to 11n 1st to Nth mixers with input signal band selection filter

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location H04B 10/02

Claims (2)

[Claims] 1. Up-converting a plurality of input baseband signals to convert them into high-frequency signals having mutually different frequencies, and then electrically / optically converting each of these high-frequency signals to generate a plurality of optical signals, An optical transmitter that optically multiplexes each of these optical signals and emits one optical signal, an optical transmission line that captures and transmits the optical signal emitted from this optical transmitter, and an optical transmission line that transmits the optical signal. An optical receiving unit for optically / electrically converting the received optical signal into a frequency-multiplexed signal, and performing optical heterodyne detection of the frequency-multiplexed signal to regenerate a plurality of baseband signals. Transmission system. 2. The optical combining transmission system according to claim 1, wherein an optical fiber amplifier is arranged in the middle of the optical transmission line.