KR20080107796A - DDM / TDM composite optical network - Google Patents

Abstract

The present invention discloses a structure of a complex optical network combining a time division multiplexing-passive optical network (TDM-PON) with a wavelength division multiplexing (WDM) technique.

The WDM / TDM composite optical network of the present invention is an optical line terminal (OLT) including a first WDM wavelength branch combiner for wavelength combining the downlink WDM individual wavelength optical signal received from the first WDM optical transceiver to generate a downlink WDM optical signal. ; A WDM-TDM conversion device for converting a downlink WDM optical signal into a downlink TDM optical signal; An optical splitter for power branching down TDM optical signals; And optical nerwork termination (ONT) for receiving a power-branched downlink TDM optical signal from an optical splitter. Compared to the conventional TDM-PON, the WDM / TDM composite optical network of the present invention has an increased transmission distance and branching rate, thereby significantly reducing network construction and operating costs.

Description

WDM / TDM Hybrid Optical Networks {WDM / TDM Hybrid Optical Networks}

1 is a diagram illustrating a conventional general TDM-PON.

Figure 2 is a conventional general WDM-PON configuration diagram.

3A is a basic configuration diagram of a WDM / TDM composite optical network.

3B is a basic configuration diagram of a WDM-TDM conversion device.

4A is a block diagram of a WDM / TDM composite optical network with optical link monitoring.

4B is a configuration diagram of a WDM-TDM conversion device having an optical link monitoring function.

FIG. 5A is a schematic diagram of a WDM / TDM composite optical network having a wavelength independent light source and a seed light source and having an optical link monitoring function. FIG.

FIG. 5B is a block diagram of a WDM-TDM conversion device including a wavelength independent light source and a seed light source and having an optical link monitoring function.

6A is a block diagram of a WDM / TDM composite optical network having a line redundancy function and an optical link monitoring function using an optical switch.

6B is a configuration diagram of a WDM-TDM conversion device having a line redundancy function and an optical link monitoring function using an optical switch.

6C is a block diagram of a WDM-TDM conversion device having a line redundancy function and an optical link monitoring function using an optical splitter.

FIG. 7A is a flow diagram of an automatic redundancy algorithm of which implements the line redundancy function in the OLT of WDM / TDM composite optical network.

7B is a flowchart of an automatic redundancy algorithm for implementing the line redundancy function in the WDM-TDM conversion apparatus of the WDM / TDM composite optical network.

8A is a configuration diagram of a WDM / TDM matching unit in a direct connection form.

8B is a configuration diagram of a WDM / TDM matching unit including a clock and data recovery unit.

The present invention relates to a complex optical network combining a time division multiplexing-passive optical network (TDM-PON) with a wavelength division multiplexing (WDM) technique.

With the recent rapid increase in Internet traffic and the convergence of broadcasting and telecommunication services, the speed of subscriber networks has been increasing rapidly. Among these technologies, passive optical network (PON) technology is introduced due to the advantages of not only providing high bandwidth to subscribers but also greatly reducing the operating cost of the network because the OSP (outside plant) consists only of passive components. This is spreading. The PON technology is classified into two types according to the difference between multiplexing and multiple access methods. The first is TDM-PON based on time division multiplexing, and the second is WDM-PON based on wavelength division multiplexing.

Figure 1 shows a schematic diagram showing a brief configuration of a conventional general TDM-PON. TDM-PON is a structure in which subscribers share optical fiber with the optical line terminal (OLT) of a national company by using time division techniques, and B-PON and G-PON standardized by ITU-T, E-PON standardized by IEEE, etc. This is currently used. Looking at the current transmission method of the general TDM-PON, one optical transceiver is installed in the optical line terminal (OLT) of the country side in terms of the downlink signal to broadcast traffic to each subscriber, A remote node (RN) uses a 1xN optical splitter that simply splits optical power, distributing the downlink optical signal transmitted from the OLT to N subscriber lines. The network termination or optical network unit (ONU) receives the downlink signal from the OLT and selectively transmits only the frames allocated to the subscriber. In the transmission of the uplink signal, the subscriber's ONT / ONU is allocated a dedicated slot in advance from the OLT through a ranging process, and then only when the time slot allocated to the subscriber arrives. When transmitting data and not in its own slot, the optical transmitter is turned off completely, and the upstream signal from each subscriber is combined in the optical node's optical splitter and sent to the OLT. In general, fixed wavelength light sources of 1480 nm to 1500 nm are used for OLT, and fixed wavelength light sources of 1260 nm to 1360 nm are used for ONT / ONU at subscriber side, but the possibility of changing the upstream and downstream wavelengths in the next-generation TDM-PON and downward Increasing bandwidth by distributing signals to optical transceivers having various wavelengths has been discussed in the standardization organization. However, TDM-PON has a problem that the transmission loss increases with the increase of the branch rate because the remote node is composed of the optical power splitter. As a result, TDM-PON has a limited bandwidth and branching rate of about 64 quarters at 2.5Gb / s shared bandwidth.

Unlike TDM-PON, which shares an optical line using time division multiplexing, the WDM-PON illustrated in FIG. 2 has a difference in sharing an optical line using a wavelength division multiplexing technique. As shown in FIG. 2, the WDM-PON logically implements a point-to-point connection by allocating dedicated uplink (λ _um ) and downlink wavelengths (λ _dm ) to M subscribers. The ranging time slot allocation process is not required. In OLT, M optical transceivers assigned to each subscriber are installed, they are combined in WDM wavelength branch combiner and transmitted by optical line, and are simply distributed to each subscriber by wavelength channel in WDM wavelength branch combiner installed in remote node. Has Although FIG. 2 illustrates a WDM-PON system for transmitting an Ethernet frame, the WDM system basically provides multiplexing at the physical layer and ensures transmission transparency at a higher layer. Thus, synchronous digital hierarchy (SDH) / It is also possible to transmit a synchronous optical network (SONET), an asynchronous transfer mode (ATM), a generic frame procedure (GFP), or the like. WDM-PON provides logical point-to-point connectivity through wavelength assignment, provides greater security than broadcast-based TDM-PON, and increases bandwidth and fiber bandwidth per fiber simply by adding wavelength. It can be increased relatively easily, but it also has the disadvantage that the light source required for WDM is relatively expensive compared to the light source for TDM-PON. As a WDM light source for WDM-PON, CWDM (coarse WDM), DWDM (dense WDM) fixed wavelength light source and DWDM wavelength independent light source are used. As a DWDM wavelength independent light source technology, a wavelength tunable laser can be used. In addition, a seed light source such as a broadband light source or a laser array is used to seed a FP (fabry-perot) laser or a reflective semiconductor optical amplifier (RSAA). And a method of spectrally dividing and injecting a light source. In addition, an optical link configuration method for generating uplink signals by remodulating downlink signals to RSOA is being researched and developed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an optical network for a subscriber network having low construction and operation costs by increasing the transmission bandwidth and the branch rate per optical fiber.

WDM Of TDM  Composite optical network

The present invention relates to a wavelength division multiplexing / time division multiplexing (WDM / TDM) composite optical network, comprising: M first WDM optical transceivers including a WDM light source and M downlink WDM individual wavelength optical signals received from the M first WDM optical transceivers. An optical line terminal (OLT) including a first WDM wavelength branch combiner for wavelength combining the signal to generate a downward WDM optical signal; A WDM-TDM conversion device for converting a downlink WDM optical signal into M downlink TDM optical signals; And an optical splitter for power branching each of the downlink TDM optical signals into N optical signals and for power coupling the uplink TDM optical signals.

In the present invention, the WDM optical transceiver uses a WDM light source, and the WDM light source includes a fixed wavelength light source and a wavelength colorless light source. In the case of using the wavelength independent light source, seed light for fixing the oscillation wavelength is required. Therefore, the seed light source and the seed light source coupling device are needed as additional components in the OLT and WDM-TDM converters. Hereinafter, an embodiment in the case of using a general WDM light source will be described with reference to the drawings, and an embodiment in the case of using a wavelength independent light source will be described.

WDM Of TDM  Transmission of Downlink Signals in a Composite Optical Network

The OLT of FIG. 3A corresponds one to one with M TDM-PON MAC & PHYs with M first WDM optical transceivers. The first WDM optical transceiver includes a WDM light source, and downlink WDM individual wavelength optical signals having M different wavelengths (λ _d1 to λ _dM ) from the first WDM optical transceiver are transmitted to the first WDM wavelength branch combiner. The wavelength is then combined into the downlink WDM optical signal. The downlink WDM optical signal is transmitted to the WDM-TDM converter, which converts the downlink WDM optical signal into M downlink TDM optical signals. Operation inside the WDM-TDM conversion apparatus will be described in detail with reference to FIG. 3B. The M downlink TDM optical signals are each transmitted to M optical splitters. Each optical splitter power splits downlink TDM optical signals into N, and the branched N downlink TDM optical signals are transmitted to the subscriber device ONT.

WDM Of TDM  Transmission of Uplink Signals in a Composite Optical Network

At the subscriber device, ONT, the uplink TDM optical signal is transmitted to the optical splitter. The optical splitter power couples the N uplink TDM optical signals transmitted from the ONT, respectively, into upstream TDM optical signals. The power coupled uplink TDM optical signal is sent to the WDM-TDM conversion device. The WDM-TDM converter converts M uplink TDM optical signals into uplink WDM optical signals through optical-to-optical conversion and transmits them to the OLT. Inside the OLT, the uplink WDM optical signal is first received at the first WDM wavelength branch combiner. The first WDM wavelength branch combiner wavelength-divides the received uplink WDM optical signal into M uplink WDM individual wavelength optical signals λ _u1 ˜ _uM . The M uplink WDM discrete wavelength optical signals are each transmitted to a first WDM optical transceiver. The first WDM optical transceiver converts the received uplink WDM individual wavelength optical signal into an electrical signal, and transmits the electrical signal to the TDM-PON OLT MAC & PHY so that the TDM-PON OLT MAC & PHY can operate.

WDM Of TDM  Transmission of Downlink Signals from Converter

3B illustrates a WDM-TDM conversion apparatus 100 according to an embodiment of the present invention. The case of the wavelength-coupled downlink WDM optical signal received from the OLT will first be discussed. The downlink WDM optical signal is received by the second WDM wavelength branch combiner 101 in the WDM-TDM conversion device 100. The second WDM wavelength branch combiner 101 splits the downlink WDM optical signal into wavelengths and _{splits the} downlink WDM optical signal into M downlink WDM individual wavelength optical signals having different wavelengths λ _d1 ˜ _dM . The downlink WDM discrete wavelength optical signal is transmitted to the second WDM optical transceiver 102. The downlink WDM individual wavelength optical signal received by the second WDM optical transceiver 102 is converted into an electrical signal and transmitted to the WDM-TDM matching unit 104. The WDM-TDM matching unit 104 receives the electrical signal and transmits it to the second TDM optical transceiver 103. The second TDM optical transceiver 103 converts the received electrical signal into a downlink TDM optical signal and transmits it to the optical splitter. The WDM-TDM matching unit 104 serves to connect the second WDM optical transceiver 102 and the second TDM optical transceiver 103, and a detailed connection relationship thereof will be described later with reference to FIGS. 8A and 8B. The second TDM optical transceiver 103 may use an optical transceiver used for a conventional TDM-PON OLT.

WDM Of TDM  Transmission of Uplink Signal from Converter

The process of transmitting the uplink TDM optical signal received from the ONT through the optical splitter by the WDM-TDM conversion apparatus 100 will be described. The uplink TDM optical signal is first received by a second TDM optical transceiver 103. The uplink TDM optical signal received by the second TDM optical transceiver 103 is converted into an electrical signal and transmitted to the WDM-TDM matching unit 104. The WDM-TDM matching unit 104 receives the electrical signal and transmits it to the second WDM optical transceiver 102. The second WDM optical transceiver 102 converts the received electrical signal into an uplink WDM discrete wavelength optical signal and transmits it to the second WDM wavelength branch combiner 101. The second WDM wavelength branch combiner 101 wavelength-couples M uplink WDM individual wavelength optical signals having different wavelengths λ _u1 ˜ _uM to the OLT.

Introduced surveillance WDM Of TDM  Composite optical network

Unlike the existing TDM-PON or WDM-PON subscriber networks, the composite optical network of the present invention has a structure in which hundreds to thousands of subscribers are accommodated in one trunk, and thus, reliability improvement of the optical link unit is greatly required. Accordingly, a function for monitoring the optical link in the trunk WDM section is required. A configuration diagram of a composite optical network incorporating such a function is shown in FIG. 4A. The WDM / TDM composite optical network of this embodiment has a separate microcontroller unit (MCU) in the OLT and the WDM-TDM converter to collect and control operation and management data of the optical module. In the OLT, the optical module means a first WDM optical transceiver, and in the WDM-TDM converter, the optical module means a second WDM optical transceiver, a WDM-TDM matching unit, and a second TDM optical transceiver.

In the WDM / TDM composite optical network, the downlink WDM optical signal is transmitted from the OLT through the WDM-TDM conversion device and the optical splitter in order to the subscriber device ONT. On the contrary, the uplink TDM optical signal is transmitted to the OLT through the optical splitter and the WDM-TDM conversion apparatus in turn from the subscriber unit ONT. Unlike the WDM / TDM composite optical network of FIGS. 3A and 3B, the OLT and the WDM-TDM converter have a separate MCU for monitoring and controlling the state of the optical module, and the optical supervisory channel (OSC) optical transceiver is λ. _uS And λ _dS Monitor and control information is exchanged through up and down light surveillance signals having wavelengths. The downlink supervisory signal is combined with the downlink WDM optical signal by the first WDM wavelength branch combiner and transmitted to the WDM-TDM converter, and the uplink supervisory signal is combined with the uplink WDM optical signal by the second WDM wavelength branch combiner and transmitted to the OLT. do.

Each of the first MCUs of the OLT is connected to each of the first M WDM optical transceivers, and collects state information regarding the following contents from the first WDM optical transceivers.

1. Output optical power and abnormal alarm of the first WDM optical transceiver

2. Receive optical power and abnormal alarm of the first WDM optical transceiver

3. Temperature and abnormal alarm of the 1st WDM optical transceiver

4. Supply voltage and abnormal alarm of the 1st WDM optical transceiver

5. Supply bias current and abnormal alarm of the first WDM optical transceiver

6. Wavelength and abnormality alarm of the first WDM optical transceiver (when using a wavelength tunable laser)

The first MCU collects state information on the above contents and controls the first WDM optical transceiver to operate normally in response to each alarm.

In addition, the first MCU receives an uplink optical monitoring signal including the optical module monitoring information inside the WDM-TDM conversion apparatus 200 from the WDM-TDM conversion apparatus 200. The optical module monitoring information inside the WDM-TDM converter 200 is collected by the second MCU 205 of the WDM-TDM converter 200 and the WDM-TDM matching unit 204. ) And the state information of the second TDM optical transceiver 203, and the details of the state information are as follows.

1. Output optical power and fault alarm of the second WDM optical transceiver 202

2. Receive optical power and abnormal alarm of the second WDM optical transceiver 202

3. Temperature and Abnormal Alarms of the Second WDM Optical Transceiver 202

4. Supply voltage and abnormal alarm of the second WDM optical transceiver 202

5. Supply Bias Current and Fault Alarm of Second WDM Optical Transceiver 202

6. Wavelength and anomaly alarm of the second WDM optical transceiver 202 (when using a wavelength tunable laser)

7. Output optical power and fault alarm of the second TDM optical transceiver 203

8. Receive optical power and abnormal alarm of the second TDM optical transceiver 203

9. Temperature and Abnormal Alarms of the Second TDM Optical Transceiver 203

10. Supply voltage and abnormal alarm of the second TDM optical transceiver 203

11. Supply bias current and fault alarm of the second TDM optical transceiver 203

The second MCU 205 collects state information on the above contents to generate an uplink optical monitoring signal, and the second OSC optical transceiver 206 transmits an uplink optical monitoring signal to the first MCU. The first MCU acquires the state information inside the above-described WDM-TDM conversion apparatus 200 based on the uplink optical monitoring signal. The first MCU generates a downlink light monitoring signal for controlling the WDM-TDM conversion device 200 in response to the information generated by the WDM-TDM conversion device 200, and the first OSC optical transceiver transmits the downlink light monitoring signal. To send.

Introduced surveillance WDM Of TDM  Transmission of Downlink Signals in a Composite Optical Network

In the OLT, the M downlink WDM individual wavelength optical signals transmitted by the M first WDM optical transceivers and the one downlink optical monitoring signal transmitted by the first OSC optical transceiver are one downlink WDM optical signal at the first WDM wavelength branch combiner. To be combined. The combined downlink WDM optical signal is transmitted to the WDM-TDM converter. The WDM-TDM converter converts the received downlink WDM optical signals into M downlink TDM optical signals. Operation inside the WDM-TDM conversion apparatus will be described in detail in the description of FIG. 4B. Downlink TDM optical signals are transmitted to M optical splitters, respectively. An optical splitter powers the received downlink TDM optical signals into N, and the power branched N downlink TDM optical signals are transmitted to N ONTs, each of which is a subscriber device.

Introduced surveillance WDM Of TDM  Transmission of Uplink Signals in a Composite Optical Network

At the subscriber device, ONT, the uplink TDM optical signal is transmitted to the optical splitter. The optical splitter power combines the N uplink TDM optical signals transmitted from the ONT into one. The power coupled uplink TDM optical signal is sent to the WDM-TDM conversion device. The WDM-TDM conversion device converts M uplink TDM optical signals into one uplink WDM optical signal through optical-to-optical conversion. The converted uplink WDM optical signal is transmitted from the WDM-TDM conversion apparatus to the OLT. Inside the OLT, the uplink WDM optical signal is received at the first WDM wavelength branch combiner. The first WDM wavelength branch combiner wavelength-divides the received uplink WDM optical signal into M upstream WDM individual wavelength optical signals λ _u1 ˜ _uM and one uplink optical monitoring signal λ _uS . The branched M uplink WDM individual wavelength optical signals are each transmitted to M first WDM optical transceivers, and one uplink optical monitoring signal is transmitted to the first OSC optical transceiver. The first WDM optical transceiver converts the received uplink WDM individual wavelength optical signal into an electrical signal, and transmits the electrical signal to the TDM-PON OLT MAC & PHY so that the TDM-PON OLT MAC & PHY can operate.

WDM Of TDM  Transmission of Downlink Signals from Converter

4B illustrates a WDM-TDM conversion apparatus 200 according to an embodiment of the present invention. The downlink WDM optical signal received from the OLT is received by the second WDM wavelength divider combiner 201 in the WDM-TDM converter 200. The second WDM wavelength branch combiner 201 wavelength-divides the downward WDM optical signal into M downward WDM individual wavelength optical signals λ _d1 to λ _dM and one downward light monitoring signal λ _dS for each wavelength. The wavelength-divided M downlink WDM discrete wavelength optical signals are each transmitted to M second WDM optical transceivers 202. The downlink WDM discrete wavelength optical signal received by the second WDM optical transceiver 202 is converted into an electrical signal and transmitted to the WDM-TDM matching unit 204. The WDM-TDM matching unit 204 receives the electrical signal and transmits it to the second TDM optical transceiver 203. The second TDM optical transceiver 203 converts the received electrical signal into a downlink TDM optical signal and transmits it to the optical splitter.

The downlink optical monitoring signal wavelength-divided at the second WDM wavelength branch combiner is received at the second OSC optical transceiver 206. The second OSC optical transceiver 206 transmits the downlink optical monitoring signal to the second MCU 205, so that the second MCU 205 transmits the second WDM optical transceiver 202 to the above description by the downlink optical monitoring signal. Control the WDM-TDM matching unit 204 and the second TDM optical transceiver 203.

WDM Of TDM  Transmission of Uplink Signal from Converter

The uplink TDM optical signal received by the WDM-TDM conversion apparatus 200 from the ONT via the optical splitter is received by the second TDM optical transceiver 203. The uplink TDM optical signal received by the second TDM optical transceiver 203 is converted into an electrical signal and transmitted to the WDM-TDM matching unit 204. The WDM-TDM matching unit 204 receives the electrical signal and transmits it to the second WDM optical transceiver 202. The second WDM optical transceiver 202 converts the received electrical signal into an uplink WDM discrete wavelength optical signal and transmits it to the second WDM wavelength branch combiner 201. The second WDM wavelength branch combiner 201 wavelength-combines the M uplink WDM individual wavelength optical signals and the uplink optical monitoring signal transmitted from the second OSC optical transceiver 206 to generate an uplink WDM optical signal, and then converts them into an OLT. send.

The second OSC optical transceiver 206 transmits an uplink optical monitoring signal including the monitoring information obtained by the second MCU 205 to the first OSC optical transceiver, and the first OSC optical transceiver transmits the uplink optical monitoring signal to the first MCU. To transmit. Thus, the first MCU controls the WDM-TDM conversion device remote from the OLT from the state information included in the uplink optical monitoring signal.

wavelength Independent  Using light source WDM Of TDM  Composite optical network

The WDM / TDM composite optical network of the present invention uses a WDM light source. Specifically, the WDM light source includes a coarse WDM (CWDM) fixed wavelength light source, a DWDM (Dense WDM) fixed wavelength light source, and a DWDM wavelength independent light source. Among them, a wavelength variable laser is used as the DWDM wavelength independent light source technology. In addition, a seed light source such as a broadband light source or a laser array is spectrally injected into a FP (Fabry-Perot) laser or a reflective semiconductor optical amplifier (RSA). Is used. In another embodiment, a wavelength-independent light source technology uses a DWDM fixed wavelength light source in an OLT, and includes an RSOA in a WDM optical transceiver of a WDM-TDM converter, and generates an uplink signal by remodulating the downlink signal light in the RSOA. Link technology is also available. Hereinafter, a case in which a wavelength independent light source is used as the WDM light source will be described.

Even when a wavelength independent light source is used, a WDM / TDM composite optical network without a monitoring function may be configured as in the embodiments of FIGS. 3A and 3B. However, in the following, since the configuration without the monitoring function can be sufficiently derived from the description of the case with the monitoring function, the configuration of the WDM / TDM composite optical network when the monitoring function is provided will be described.

In particular, in the embodiments of FIGS. 5A and 5B, a WDM / TDM composite optical network using an A-band seed light source and an upward signal light using a B-band seed light source will be described.

In the WDM / TDM composite optical network of FIG. 5A, the downlink signal is transmitted from the OLT to the subscriber device ONT through the WDM-TDM conversion device and the optical splitter. On the contrary, the uplink signal is transmitted to the OLT through the optical splitter and the WDM-TDM conversion device in order from the subscriber device ONT. In addition, OLT and WDM-TDM converters have separate MCU and OSC optical transceivers for monitoring. In the OLT, the oscillation wavelength of the downlink WDM optical signal is fixed by using the A-band seed light, and the oscillation wavelength of the uplink WDM optical signal is fixed by the B-nand seed light in the WDM-TDM converter.

Referring to the components of the OLT 300 in the present embodiment, first, M TDM-PON MAC & PHYs are respectively connected to M first WDM optical transceivers 303 in the OLT 300. The first WDM optical transceiver 303 includes a wavelength independent light source, and FP laser, RSOA, or the like may be used for the wavelength independent light source. The first WDM optical transceiver 303 is connected to the first WDM wavelength branch combiner 302. The first WDM wavelength branch combiner 302 is connected to the first seed light source combiner 301 for A-band, and the first seed light source combiner 301 for A-band is an A-band seed light source 305. Connected with The first MCU 304 is connected to the M first WDM optical transceivers 303 and the A-band seed light sources 305, respectively, to collect state information of the OLT internal optical module.

1. Output optical power and abnormal alarm of the first WDM optical transceiver 303

2. Receive optical power and abnormal alarm of the first WDM optical transceiver 303

3. Temperature and abnormality alarm of the first WDM optical transceiver 303

4. Supply voltage and abnormal alarm of the first WDM optical transceiver 303

5. Supply Bias Current and Abnormal Alarm of First WDM Optical Transceiver 303

6. Wavelength and abnormality alarm of the first WDM optical transceiver 303 (when using a wavelength tunable laser)

7. Output optical power and abnormal alarm of A-band seed light source 305

8. Internal temperature and abnormality alarm of A-band seed light source 305

wavelength Independent  Using light source WDM Of TDM  Transmission of Downlink Signals in a Composite Optical Network

In the OLT 300 of FIG. 5A, the A-band seed light source coupling device 301 transmits the A-band seed light generated by the A-band seed light source 305 to the first WDM wavelength branch combiner 302. . The first WDM wavelength branch combiner 302 spectrally divides the input A-band seed light and transmits it to the first WDM optical transceiver 303. In the first WDM optical transceiver 303, the output wavelength of the wavelength independent light source is fixed by the spectrum-divided A-band seed light, and the downlink WDM individual wavelength optical signal is output. M downlink WDM individual wavelength optical signals having different wavelengths λ _d1 to λ _dM outputted from the M first WDM optical transceivers 303, and wavelengths of λ _dS outputted from the first OSC optical transceiver 306. The downlink optical monitoring signal is coupled to the downlink WDM optical signal by the first WDM wavelength branch combiner 302, and the downlink WDM optical signal is passed through the seed light source coupling device 301 for A-band to the WDM-TDM conversion apparatus 400. Is sent to.

The downlink WDM optical signal received by the WDM-TDM conversion apparatus 400 is optical-to-optically converted into M downlink TDM optical signals. Operation inside the WDM-TDM conversion apparatus will be described in detail in the description of FIG. 5B. Downlink TDM optical signals output from the WDM-TDM conversion apparatus 400 are transmitted to M optical splitters, respectively. The optical splitter power-branches each received downlink TDM optical signal into N, and the power-branched N downlink TDM optical signals are transmitted to N ONTs, each of which is a subscriber device.

wavelength Independent  Using light source WDM Of TDM  Transmission of Uplink Signals in a Composite Optical Network

At the subscriber device, ONT, the uplink TDM optical signal is transmitted to the optical splitter. The optical splitter power combines the N upstream TDM optical signals received from the ONT into one, respectively. The power coupled uplink TDM optical signal is received by the WDM-TDM conversion device 400. The WDM-TDM conversion apparatus 400 converts the received M uplink TDM optical signals into uplink WDM optical signals through optical-to-optical conversion and transmits them to the OLT 300. Operation of the WDM-TDM conversion apparatus 400 will be described in detail with reference to FIG. 5B.

Inside the OLT 300, the upward WDM optical signal passes through the first seed light source coupling device 301 for A-band and is received by the first WDM wavelength branch combiner 302. The first WDM wavelength branch coupler 302 ) Splits one uplink WDM optical signal into M uplink WDM individual wavelength optical signals having different wavelengths (λ _u1 to λ _uM ) and an uplink optical monitoring signal having a wavelength of λ _uS . The branched M uplink WDM discrete wavelength optical signals are each transmitted to the M first WDM optical transceivers 303. The first WDM optical transceiver 303 converts the received uplink WDM individual wavelength optical signal into an electrical signal and transmits the electrical signal to the TDM-PON OLT MAC & PHY so that the TDM-PON OLT MAC & PHY can operate. Make sure

The first OSC optical transceiver 306 transmits the uplink optical monitoring signal wavelength-divided by the first WDM wavelength branch combiner 302 to the first MCU 304. The first MCU 304 collects state information inside the WDM-TDM conversion device 400 included in the uplink optical monitoring signal and controls the WDM-TDM conversion device 400 remotely.

WDM - TDM  Transmission of Downlink Signals from Converter

5B illustrates a WDM-TDM conversion apparatus 400 according to an embodiment of the present invention. The downlink WDM optical signal received from the OLT passes through the second seed light source coupling device 401 for B-band and is transmitted to the second WDM wavelength branch combiner 402. The second WDM wavelength branch combiner 402 wavelength-differentiates the downlink WDM optical signal, so that the M downlink WDM individual wavelength optical signals having different wavelengths (λ _d1 to λ _dM ) and the downlink optical monitoring signal having a wavelength of λ _dS Generates. The wavelength-divided M downlink WDM individual wavelength optical signals are each transmitted to the M second WDM optical transceivers 403. The downlink WDM individual wavelength optical signal received by the second WDM optical transceiver 403 is converted into an electrical signal and transmitted to the WDM-TDM matching unit 405. The WDM-TDM matching unit 405 receives the electrical signal and transmits it to the second TDM optical transceiver 407. The second TDM optical transceiver 407 converts the received electrical signal into a downlink TDM optical signal and transmits it to the optical splitter.

The downlink optical monitoring signal wavelength-divided at the second WDM wavelength branch combiner 402 is received by the second OSC optical transceiver 406. The second OSC optical transceiver 406 transmits the downlink optical monitoring signal to the second MCU 404, so that the second MCU 404 matches the second WDM optical transceiver 403, WDM-TDM by the downlink optical monitoring signal. The unit 405 and the second TDM optical transceiver 407 are controlled.

WDM - TDM  Transmission of Uplink Signal from Converter

The operation of the WDM-TDM conversion apparatus 400 in the case of an uplink TDM optical signal received through the optical splitter from the ONT will be described. The uplink TDM optical signal is first received by a second TDM optical transceiver 407. The uplink TDM optical signal received by the second TDM optical transceiver 407 is converted into an electrical signal and transmitted to the WDM-TDM matching unit 405. The WDM-TDM matching unit 405 receives the electrical signal and transmits it to the second WDM optical transceiver 403.

The second WDM optical transceiver 403 converts the received electrical signal into an uplink WDM individual wavelength optical signal using a wavelength independent light source and transmits it to the second wavelength branch combiner 402, which is described below using a wavelength independent light source. The process of fixing the output wavelength in the second WDM optical transceiver 402 will be described. First, the B-band seed light source coupling device 403 transmits the B-band seed light generated from the B-band seed light source 408 to the second WDM wavelength branch combiner 402. The second WDM wavelength branch combiner transmits the input B-band seed light by spectral division to the second WDM optical transceiver 403. In the second WDM optical transceiver 403, the output wavelength of the wavelength independent light source is fixed by the spectral-divided B-band seed light, and an uplink WDM individual wavelength optical signal is output. The M uplink WDM individual wavelength optical signals having different wavelengths λ _u1 to λ _uM are transmitted to a second WDM wavelength branch combiner.

The second WDM wavelength branch combiner 402 has M uplink WDM individual wavelength optical signals having different wavelengths λ _u1 to λ _uM and upward light having a wavelength of λ _uS transmitted from the second OSC optical transceiver 406. The supervisory signal is wavelength coupled to generate an upward WDM optical signal. The uplink WDM optical signal is transmitted to the OLT 300 through the seed light source coupling device 401 for B-band.

Referring to the role of the second MCU 404 and the second OSC optical transceiver 406 in the uplink signal transmission, the second MCU 404 is a second WDM optical transceiver 403, WDM-TDM matching unit 405 ) Are connected to the B-band seed light source 408 and the second TDM optical transceiver 407, respectively, to monitor the status of each device and to transmit the monitored status information to the second OSC optical transceiver 406. The contents monitored and alerted by the second MCU 404 are as follows.

1. Output optical power and abnormal alarm of the second WDM optical transceiver 403

2. Receive optical power and abnormal alarm of the second WDM optical transceiver 403

3. Temperature and abnormality alarm of the second WDM optical transceiver 403

4. Supply voltage and abnormal alarm of the second WDM optical transceiver 403

5. Supply Bias Current and Abnormal Alarm of Second WDM Optical Transceiver 403

6. Wavelength and abnormality alarm of the second WDM optical transceiver 403 (when using a wavelength tunable laser)

7. Output optical power and fault alarm of the second TDM optical transceiver 407

8. Receive optical power and abnormal alarm of the second TDM optical transceiver 407

9. Temperature and Abnormal Alarms of the Second TDM Optical Transceiver 407

10. Supply voltage and abnormal alarm of the second TDM optical transceiver 407

11. Supply bias current and fault alarm of the second TDM optical transceiver 407

12. Output optical power and fault alarm of the B-band seed light source 408

13. Internal temperature and abnormality alarm of B-band seed light source 408

The second OSC optical transceiver 406 transmits an uplink optical monitoring signal including the monitoring information obtained by the second MCU 404 to the first OSC optical transceiver 306, and the first OSC optical transceiver 306 is an uplink optical. The monitoring signal is transmitted to the first MCU 304. Thus, the first MCU 304 may manage the WDM-TDM conversion device 400 remote from the OLT 300 from the state information included in the uplink optical monitoring signal.

When the wavelength independent light source technology is applied to a WDM / TDM composite optical network, the light source of both phase and downward may be configured as a wavelength independent light source, but only one of the phase and downward light uses a wavelength independent light source, and the other It is also possible to use a fixed wavelength light source. It is also possible to use a wavelength independent light source for the first OSC optical transceiver 306 or the second OSC optical transceiver 406.

Introduced optical line redundancy WDM Of TDM  Composite optical network

FIG. 6A illustrates the structure of a WDM / TDM composite optical network in which an optical line redundancy function is introduced to further improve the reliability of the optical link and to cope with a failure quickly. Compared to FIG. 4A, a 1 × 2 first optical switch 503 is added to the rear end of the OLT 500, and the first MCU 504 of the OLT is in charge of controlling the first optical switch 503. In addition, in FIG. 6B, a 1 × 2 second optical switch 603 is added to the front of the WDM-TDM converter 600 compared to FIG. 4B, and the control of the second optical switch 603 is controlled by the WDM-TDM converter 600. 2 MCU 602 is in charge. Hereinafter, the operation of the optical switch together with the algorithm of FIGS. 7A and 7B will be described.

7A illustrates an embodiment of a first optical switch 503 redundancy control algorithm 700 of the OLT 500. The first optical switch 503 is normally connected to port a so that the optical signal is transmitted to the working fiber (step 701). The uplink WDM individual wavelength optical signal is transmitted from all the first WDM optical transceivers 502. If not, the first MCU 504 monitoring the first WDM optical transceiver 502 determines that the reception of all channels is abnormal. (Step 702) If the reception of all channels is abnormal, the first MCU 504 The first optical switch 503 is changed to port b so that transmission is performed to the protection fiber (step 703). Similarly, the first optical switch 503 is normally connected to port b. When an optical signal is transmitted on the protection line, if reception error of all channels occurs (step 704), the first MCU 504 changes the first optical switch 503 from port b to port a to protect the protection line. (Step 705) The operation line and the protection line are made to the main line. And to sense the two lines, along as well, the concept of the secondary (sub) line. Therefore, if the optical signal can be transmitted on either the protective line or the operating line, the whole network is operating normally.

In FIG. 7B, the second optical switch 603 is normally connected to port a so that an optical signal is transmitted to the operation line. (Step 711) Downward WDM individual wavelength optical signals are received by all the second WDM optical transceivers 602. If not, the second MCU 604 monitoring the second WDM optical transceiver 602 determines that the reception of all the channels is abnormal. (Step 712) If the reception of all the channels is abnormal, the second MCU 604 first. 2 The optical switch 603 is changed to port b so that transmission is performed to the protection line. (Step 713) Similarly, the first optical switch 603 is normally connected to port b so that an optical signal is transmitted from the protection line. In the case of transmission, if reception error of all channels occurs (step 714), the second MCU 604 changes the second optical switch 603 from port b to port a so that transmission from the protection line to the operation line is stopped. (Step 715).

The first optical switch 503 and the second optical switch 603 are switched from the operation line to the protection line or the protection line to the operation line by the algorithm of FIGS. 7A and 7B, respectively, in the event of an abnormal reception of all channels. Is done. Although a separate signal for interworking is not transmitted between the first optical switch 503 and the second optical switch 603, since the switching is performed under the same conditions, the first optical switch 503 and the second optical switch ( 603 behaves as if it is interlocked. In addition, by appropriately setting the waiting time (w, x, y, z) before the switching is made, it is possible to achieve stability of the switching connection between the OLT 500 and the WDM-TDM converter 600.

This redundancy technique can also be applied to the composite optical network 300 using the wavelength independent light source and the seed light source shown in FIGS. 5A and 5B. In this embodiment, the position of the first optical switch is the rear end of the OLT 300, that is, the rear end of the first seed light source coupling device 301 for A-band. The position of the second optical switch is the front end of the WDM-TDM conversion device 400, that is, the front end of the second seed light source coupling device 401 for B-band. In this embodiment, the optical switch is switched from the operation line to the protection line or from the protection line to the operation line when reception abnormality occurs in all channels according to the algorithm of FIGS. 7A and 7B. In addition, by appropriately setting the waiting time (w, x, y, z) before the switching is performed, the stability of the switching connection between the OLT and the WDM-TDM converter can be achieved.

6C illustrates another embodiment of WDM / TDM composite optical network fiber redundancy. In this embodiment, an optical switch is used only for the OLT, and a 1: 2 splitter having a power branching ratio of 50:50 is used for the WDM-TDM converter. In this case, the downlink signal flows to only one of the operation line or the protection line according to the optical switch connection direction of the OLT, but the upstream signal flows to both the operation line and the protection line. In this case, however, since the splitter is a passive element, the control of the second MCU becomes impossible, and the recovery process by the above-described algorithm is performed only in the OLT. That is, the optical switch of the OLT is operated as it is by the algorithm of FIG.

WDM - TDM Matching part

The WDM-TDM matching unit, which is a building block in the WDM-TDM conversion apparatus, may be variously implemented according to the conditions of the optical link, and the embodiment is illustrated in FIGS. 8A and 8B. FIG. 8A illustrates an embodiment of a directly connected WDM-TDM matching unit 800, in which the optical signal transmission paths of the second WDM optical transceiver 801 and the second TDM optical transceiver 802 are directly bound. The downlink WDM discrete wavelength optical signal (or downlink WDM discrete wavelength optical signal) is received and photo-converted at the receiver 803 of the second WDM optical transceiver to generate an electrical signal (typically a differential signal). The electrical signal is transmitted to the transmitter 805 of the second TDM optical transceiver via the WDM-TDM matcher 800. The transmitting unit 805 of the second TDM optical transceiver converts the electrical signal into a downlink TDM optical signal and transmits it to the optical splitter.

In the case of an uplink signal, the receiver 806 of the second TDM optical transceiver receives and up-converts the uplink TDM optical signal from the optical splitter to generate an electrical signal. The electrical signal is transmitted to the transmitter 804 of the second WDM optical transceiver via the WDM-TDM matcher 800. The transmitter 804 of the second WDM optical transceiver converts the electrical signal into an uplink WDM individual wavelength optical signal and transmits it to the second WDM wavelength branch combiner.

8B shows a WDM-TDM matching unit 900 including a clock and data recovery unit 903 between a second WDM optical transceiver 901 and a second TDM optical transceiver 902. The process of transmitting the signal is the same as that of FIG. 8A, and the distortion and jitter are removed while the electric signal passing through the WDM-TDM matching unit 900 passes through the clock and data recovery unit 903. The clock and data recovery unit 903 may be implemented by adding a separate chip, and may be implemented using a built-in function of a conventional PHY chip or a serializer / deserializer (SERDES) chip.

The present invention is a WDM / TDM composite optical network, since the power branched to N in the TDM method again after being wavelength-divided into the M in the WDM method, the total branching rate is M x N, so that the existing TDM-PON or WDM A significant increase in branching rates can be achieved compared to optical networks consisting of -PON alone. For example, when the WDM 16 branch and the TDM-PON 32 branch are combined, the total branch rate is 512 branches, which can accommodate 512 subscribers simultaneously on one fiber.

In addition, since the optical link is divided into a WDM-PON section and a TDM-PON section centering on the WDM-TDM converter, it is easy to increase the transmission distance compared to the existing TDM-PON or WDM-PON.

ONT, a subscriber device, is compatible with existing TDM-PON and easily upgrades a subscriber network composed of the existing TDM-PON to the WDM / TDM composite optical network of the present invention. Therefore, the cost of building a WDM / TDM composite optical network can be reduced.

In a WDM / TDM composite optical network with optical monitoring, the OLT can control remote nodes, so even if there are hundreds to thousands of subscribers per trunk, the OLT can control it. Therefore, the reliability of the optical link portion is improved.

In a WDM / TDM composite optical network using a wavelength independent light source and a seed light source, both uplink WDM optical signals are generated in the WDM-TDM converter, and the WDM-TDM converter must have power for optical-to-optical conversion. Since it is supplied, it is possible to configure the seed light source for generating the uplink optical signal in the WDM-TDM conversion device. In addition, by placing the seed light source at a remote node other than the OLT, there is no need to compensate the optical path loss, so that the seed light source can use a seed light source having a lower power than the WDM-PON focused only on the OLT. Therefore, even when using a wavelength independent light source provided with a seed light source in the WDM interval of the present invention, it is easy to increase the transmission distance of the WDM interval than the existing WDM-PON.

Claims (15)

A wavelength division multiplexing / time division multiplexing (WDM / TDM) composite optical network, M first WDM optical transceivers comprising a WDM light source and a first WDM wavelength branch combiner for wavelength-combining the M down WDM individual wavelength optical signals received from the M first WDM optical transceivers to generate a downward WDM optical signal. An optical line terminal (OLT); A WDM-TDM conversion device for converting the downlink WDM optical signals into M downlink TDM optical signals; And And an optical splitter for power branching each of the downlink TDM optical signals into N optical signals and for power coupling the uplink TDM optical signals. The method of claim 1, The WDM-TDM conversion device, A second WDM wavelength branch combiner for wavelength-dividing the downlink WDM optical signal to generate M downlink WDM individual wavelength optical signals; A second WDM optical transceiver for receiving said downlink WDM discrete wavelength optical signal and converting it into a downlink electrical signal; A second TDM optical transceiver for converting the downlink electrical signal into a downlink TDM optical signal; And And a WDM-TDM matching unit connecting the second WDM optical transceiver and the second TDM optical transceiver. The method of claim 2, And the WDM-TDM matching unit directly connects the second WDM optical transceiver with the second TDM optical transceiver. The method of claim 2, The WDM-TDM matching unit further comprises a clock and data recovery unit between the second WDM optical transceiver and the second TDM optical transceiver. The method of claim 1, The OLT is, Collecting the state information of the first WDM optical transceiver to control the first WDM optical transceiver to operate normally; And a first microcontroller unit (MCU) for generating a downlink optical monitoring signal based on state information of the WDM-TDM converter to control the WDM-TDM converter to operate normally. The method of claim 5, wherein The WDM-TDM conversion device, Generate and provide an uplink light monitoring signal to the first MCU based on the state information of the WDM-TDM conversion device, and the WDM-TDM conversion device operates normally by the downlink light monitoring signal received from the first MCU. WDM-TDM composite optical network device further comprising a second MCU to control to. The method of claim 5, wherein The OLT further comprises a first optical supervisory channel (OSC) optical transceiver for transmitting the downlink optical monitoring signal to the WDM-TDM conversion device. The method of claim 6, The WDM-TDM conversion apparatus further comprises a second OSC optical transceiver for transmitting the uplink optical monitoring signal to the OLT. The method of claim 1, WDM / TDM composite optical network, A first optical switch located at the rear end of the OLT and switched when upstream WDM individual wavelength optical signals are not simultaneously received at the first WDM optical transceiver of all wavelength channels; And And a second optical switch located in front of the WDM-TDM converter and switched when the downstream WDM discrete wavelength optical signal is not simultaneously received at the second WDM optical transceiver of all wavelength channels. Device. The method of claim 1, WDM / TDM composite optical network, A first optical switch located at a rear end of the OLT and switched when an uplink WDM discrete wavelength optical signal is not simultaneously received at the first WDM optical transceiver of all wavelength channels; And And an optical splitter positioned in front of said WDM-TDM converter, said optical splitter for power coupling an operational line and a protective line. The method of claim 1, The OLT is, An A-band seed light source for supplying A-band seed light for fixing an oscillation wavelength of the wavelength independent light source to use a wavelengthless color light source in the first WDM optical transceiver; And And a first seed light source combining device for A-band for transmitting the A-band seed light to the first WDM optical transceiver. The method of claim 2, The WDM-TDM conversion device, A B-band seed light source for supplying a B-band seed light for fixing an oscillation wavelength of the wavelength independent light source to use a wavelength independent light source for the second WDM optical transceiver; And And a second seed light source combining device for B-band that transmits the B-band seed light to the second WDM optical transceiver. The method of claim 11, The OLT is, Collecting the state information of the first WDM optical transceiver and the A-band seed light source to control the first WDM optical transceiver to operate normally; And a first MCU generating a downlink optical monitoring signal based on the state information of the WDM-TDM converter to control the WDM-TDM converter to operate normally. The method of claim 12, The WDM-TDM conversion device, Collecting state information of the second WDM optical transceiver and the B-band seed light source to generate an uplink optical monitoring signal to provide to the first MCU, the WDM-TDM by the downlink optical monitoring signal received from the first MCU The WDM-TDM composite optical network device further comprising a second MCU for controlling the converter to operate normally. The method of claim 1, The uplink and downlink TDM optical signal protocol is a point-to-multipoint connection based TDM-PON signal, WDM / TDM composite optical network device.

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