JP2006074629A - Wavelength-multiplexing optical receiver unit and optical communication system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wavelength-multiplexing optical receiver unit and an optical communication system using the wavelength-multiplexing optical receiver unit, realizing highly sensitive reception and excellent expandability, with a low initial installation cost. <P>SOLUTION: An optical transmitter (30) includes one or a plurality of optical transmitters (140-1) for transmitting optical signals of non-overlapped frequencies, and an optical multiplexer (141) for multiplexing the optical signals received from the optical transmitter and making a wavelength-multiplexed optical signal incident into an optical fiber. An optical receiver unit (200) includes: an optical demultiplexer (210) for demultiplexing the wavelength-multiplexed optical signal being input via the optical fiber into one or a plurality of optical signals on a basis of each the above frequency; an optical amplifier (221) for amplifying one optical signal among the optical signals demultiplexed in the optical demultiplexer to desired optical power; a variable wavelength optical band-pass filter (222) for transmitting the optical signal amplified in the optical amplifier; and one or a plurality of optical reception means (220-1) each having an optical receiver (223) for receiving the optical signal transmitted through the variable wavelength optical band-pass filter. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical receiver of a wavelength division multiplexing optical communication system.

  Rare earth doped optical fiber amplifiers (hereinafter referred to as optical fiber amplifiers) are widely used in optical communication systems. In a wavelength division multiplexing optical communication system, the optical power of an optical signal attenuated as it propagates in an optical fiber is collectively amplified as an optical signal in an optical fiber amplifier without being converted into an electrical signal. The optical signal transmission distance in the optical communication system is markedly improved by disposing the optical fiber amplifier between the optical signal transmitter and the optical signal receiver as compared with the case where the optical fiber amplifier is not used.

  In general, such an optical fiber amplifier is provided with a gain control function that always keeps the output power of an optical signal constant in order to maintain a desired transmission quality. In a wavelength division multiplexing optical communication system, the number of wavelengths passing through an optical fiber amplifier may fluctuate due to an increase or decrease in the number of channels or a device failure. Even when the number of wavelengths varies in this way, the output power of the optical signal for each channel passing through the optical fiber amplifier must be kept constant. That is, the reception power of the optical signal for each channel received by the optical signal receiver must be kept constant.

Therefore, as a gain control method suitable for such a wavelength division multiplexing optical communication system, even if the total input power of the optical signal input to the optical fiber amplifier changes, the gain constant control method can keep the gain constant. Has been proposed. (For example, see Non-Patent Document 3)
On the other hand, the propagation loss (loss) of the optical power of the optical signal propagating in the actually installed optical fiber is the difference in the optical fiber length, the dispersion of the connection loss at the optical fiber connection point, or the aging of the optical fiber. For reasons such as the above, it is not necessarily constant. Therefore, there is a known gain control method that can compensate not only for fluctuations in the output power of the optical fiber amplifier due to fluctuations in the number of wavelengths but also for fluctuations in propagation loss and to keep the output level of the optical signal for each channel constant. ing. (For example, see Non-Patent Documents 1 and 2)
FIG. 1 shows a configuration example of a wavelength division multiplexing communication system 10 using an optical receiver 20 for a wavelength division multiplexing communication system equipped with a conventional optical fiber amplifier 100.

  A wavelength division multiplexing communication system 10 illustrated in FIG. 1 includes an optical transmitter 30 and an optical receiver 20 connected to the optical transmitter 30 via an optical fiber 150. The optical transmitter includes a plurality of optical transmitters 140-1, 140-2,... That output light having different wavelengths, and a fixed wavelength that combines the output light from each optical transmitter and outputs the resultant light to the optical fiber 150. And an optical multiplexer 141. A conventional optical receiver 20 for a wavelength division multiplexing communication system includes an optical fiber amplifier 102 whose gain is controlled by a constant gain control circuit (AGC) 101, a gain equalizer 103 for flattening the gain of the optical fiber amplifier 102, a variable From the outputs of the gain-flattened WDM pre-optical amplifier 100 and the gain-flattened WDM pre-optical amplifier 100 provided with the optical output power constant control circuit 105 for feedback control of the optical attenuator 104 and the variable optical attenuator 104, respectively. The optical demultiplexer 120 which isolate | separates the optical signal from which a wavelength differs, and optical receiver 130-1,130-2, ... are provided. The gain-flattened WDM pre-amplifier 100 branches the optical signal input from the optical fiber 150, and uses one optical signal as an input to the optical fiber amplifier 102 and the other as an input to the photodiode 107. The optical signal from the coupler 106 and the variable optical attenuator 104 is branched, and one is input to the optical demultiplexer 120 and the other is input to the photodiode 109 connected to the optical output power constant control circuit 105. It further includes an optical coupler 108, a photodiode 107, a constant gain control circuit 101, and a monitoring circuit 110 connected to the constant optical output power control circuit 105. In such a configuration, fluctuations in the number of wavelengths and span loss fluctuations can be compensated, and gain flatness can be maintained because the gain in the optical fiber amplifier 102 does not change.

Suzuki et al. "Linear optical repeater gain control in WDM bus networks" Society Conference ('97) Yoshida et al. "Output level control method for WDM optical amplifier" Society Society Conference ('96) Sakurai et al. “Study on configuration method of wavelength-multiplexed fiber optic amplifier” IEICE Technical Report OCS95-36

  However, in general, the gain flattening WDM pre-amplifier requires uniform characteristics over a wide wavelength range of about 20 to 30 nm, and therefore requires a very precise gain equalizer. In addition, since the design of this gain equalizer changes depending on the signal input power to the optical amplifier, the required gain, etc., it is unsuitable for mass production and it is difficult to reduce the price. Even when the optical signal transmitted in the wavelength division multiplexing communication system is only one wavelength (one channel), such an expensive optical fiber amplifier is necessary. There wasn't. When applied to an access network, an optical receiver that has low initial introduction cost, has excellent expandability, and realizes high-sensitivity reception has been required.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an optical receiver that realizes high-sensitivity reception with low initial introduction cost and excellent expandability. .

  In order to achieve the above object, the present invention provides an optical receiver connected to an optical transmitter via an optical fiber, wherein the optical receiver has one or more non-overlapping wavelengths. A wavelength-multiplexed optical signal obtained by wavelength-multiplexing a plurality of optical signals is demultiplexed by a wavelength-demultiplexed optical demultiplexer that demultiplexes one or more optical signals for each wavelength, and the optical demultiplexer. An optical amplifier that amplifies one of the optical signals to a desired optical power, an optical bandpass filter that transmits the optical signal amplified by the optical amplification means, and the optical bandpass filter that transmits the optical signal And one or a plurality of optical receiving means having an optical receiver for receiving an optical signal.

  A second aspect of the present invention is the optical receiver according to the first aspect, wherein the optical bandpass filter is a tunable optical bandpass filter.

  A third aspect of the present invention is the optical receiver according to the second aspect, wherein the tunable optical bandpass filter has a full width at half maximum of a transmission wavelength of 5 nm or less.

A fourth aspect of the present invention is the optical receiver according to any one of the first to third aspects, wherein the optical demultiplexer is an arrayed waveguide grating having a first input and a second input. And demultiplexing optical signals of frequencies f ₀ and f ₀ ± Δf from the frequency-multiplexed optical signal input to the first input and the second frequency-multiplexed optical signal input to the second input, respectively. The same port output, the frequency of the center wavelength of the transmission wavelength in the optical bandpass filter is f ₀ ± Δf / 2, and the full width at half maximum of the transmission wavelength is Δf or more.

  The invention according to claim 5 is an optical communication system comprising an optical transmission device, an optical fiber, and an optical reception device, wherein the optical transmission device transmits one or a plurality of optical signals that transmit optical signals having non-overlapping frequencies. A transmitter, and an optical multiplexer that multiplexes the optical signals from the optical transmitter and enters a wavelength-multiplexed optical signal into the optical fiber, and the optical receiver is input via the optical fiber An optical demultiplexer that demultiplexes the wavelength-multiplexed optical signal into one or more optical signals for each frequency, and one optical signal among the optical signals demultiplexed by the optical demultiplexer is desired. One or more optical amplifiers that amplify to optical power, an optical bandpass filter that transmits the optical signal amplified by the optical amplifier, and an optical receiver that receives the optical signal transmitted through the optical bandpass filter Light receiver Characterized by comprising a means.

The invention according to claim 6 is an optical communication system in which a first optical transmission device and a second optical transmission device are connected to an optical reception device via a first optical fiber and a second optical fiber, respectively. The first optical transmission device multiplexes one or a plurality of first optical transmitters that transmit optical signals having non-overlapping frequencies, and the optical signals from the first transmitter to perform first wavelength multiplexing. A first optical multiplexer for inputting an optical signal to the first optical fiber is provided, and the second optical transmitter is a light having a frequency shifted by Δf from the frequency of the optical signal transmitted by each of the first optical transmitters. One or a plurality of second optical transmitters that respectively transmit signals, and a second wavelength-multiplexed optical signal that enters the second optical fiber by combining the optical signals from the second transmitter. The optical receiver includes an array having a first input and a second input. A waveguide grating, the first of the first frequency-multiplexed optical signal inputted to the input and the second from the second frequency-multiplexed optical signal is input to the input, the optical signal of each frequency f ₀ and f ₀ ± Delta] f Is demultiplexed and output to the same port, an optical amplifier for amplifying one of the optical signals demultiplexed by the optical demultiplexer, and amplified by the optical amplification means And an optical band-pass filter that transmits the optical signal, and one or a plurality of optical receiving units that include an optical receiver that receives the optical signal transmitted through the optical band-pass filter.

  A seventh aspect of the present invention is the optical communication system according to the fifth or sixth aspect, wherein the optical bandpass filter is a tunable optical bandpass filter.

  The invention according to claim 8 is the optical communication system according to claim 7, wherein the wavelength tunable optical bandpass filter has a full width at half maximum of a transmission wavelength of 5 nm or less.

The invention according to claim 9 is the optical communication system according to claim 7 or 8, wherein the frequency of the center wavelength of the transmission wavelength in the wavelength tunable optical bandpass filter is f ₀ ± Δf / 2. The full width at half maximum of transmission is Δf or more.

  According to the present invention, it is possible to realize an optical receiver that realizes high-sensitivity reception with low initial introduction cost and excellent expandability, and a wavelength multiplexing communication system using the optical receiver.

  Embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 2 shows a wavelength division multiplexing communication system 10 according to Embodiment 1 of the present invention. The wavelength division multiplexing communication system 10 includes an optical transmitter 30 and an optical receiver 200 connected to the optical transmitter 30 via an optical fiber 150. The configuration of the optical transmission device 30 is the same as the configuration of the optical transmission device used in the conventional wavelength division multiplexing communication system described with reference to FIG. The optical receiver 200 amplifies the single wavelength optical signal separated by the optical demultiplexer 210 and the fixed wavelength demultiplexer 210 that separates the input wavelength division multiplexed (WDM) optical signal for each wavelength. A single-channel optical amplifier 221, an optical signal from the wavelength variable optical bandpass filter 222 for removing amplified spontaneous emission noise (ASE noise) generated in the optical amplifier 221, and an optical signal from the wavelength variable optical bandpass filter 222 are input. Are provided with a plurality of wavelength-independent optical receivers 220-1, 220-2,. The wavelength-independent optical receivers 220-1, 220-2,... Branch the optical signal separated into a single wavelength by the optical demultiplexer 210, use one optical signal as an input to the optical amplifier 221, and the other as the input. An optical coupler 226 to be input to the photodiode 227 and an optical signal from the optical amplifier 221 are branched, one is input to the wavelength tunable optical bandpass filter 222, and the other is connected to the optical output power constant control circuit 224. An optical coupler 228 that is input to the photodiode 229 and an optical signal from the wavelength tunable optical bandpass filter 222 are branched, one of which is input to the optical receiver 223 and the other is connected to the wavelength control circuit 225. Connected to an optical coupler 230 as an input to the diode 231, a photodiode 227, a constant output power control circuit 224, and a wavelength control circuit 225 Viewing further comprises a circuit 232.

  The photodiode 227 is used, for example, for detecting the presence or absence of an input signal from the optical demultiplexer 210 in the monitoring circuit 232. The photodiode 229 is used, for example, to control the output of the optical amplifier 221 in an output constant control circuit. The photodiode 231 is used, for example, to control the transmission wavelength of the wavelength tunable optical bandpass filter 222 in the wavelength control circuit 225.

  The wavelength multiplexed optical signal input to the optical receiver 200 via the optical fiber 150 is separated into wavelengths by the optical demultiplexer 210, amplified by the optical amplifier 221, and ASE by the wavelength tunable optical bandpass filter 222. Noise is removed and input to the optical receiver.

  The first feature of the present invention is that the optical amplifier 221 is arranged not at the front stage of the optical demultiplexer 210 but at the rear stage. By disposing the optical amplifier 221 at the subsequent stage of the optical demultiplexer 210, the optical signal input to the optical amplifier always has a single wavelength, so that the gain equalizer 103 as shown in FIG. Thus, an inexpensive single channel optical amplifier can be used without the need for a gain flattening WDM pre-amplifier. Inexpensive single-channel optical amplifiers include semiconductor optical amplifiers (SOA) and waveguide optical amplifiers. A rare earth-doped optical fiber amplifier for metro that can be used in a narrow wavelength band of about 5 to 10 nm can also be used for single-channel amplification.

  The second feature of the present invention is that a wavelength tunable optical bandpass filter 222 is disposed after the optical amplifier 221. The tunable optical bandpass filter 222 can remove ASE noise from an optical signal having a single wavelength, thereby realizing high-sensitivity reception. By making the wavelength of the optical bandpass filter variable, the wavelength independent optical receivers 220-1, 220-2,... In the optical receiver 200 are made into a single product, and it is necessary to have many products in stock. Since it is not available, the cost can be reduced in the future, and it has the advantages of excellent expansion.

  The initial setting algorithm of the transmission wavelength of the tunable optical bandpass filter 222 will be described later.

FIG. 3 shows simulation and experimental results for the filter width of the wavelength tunable optical bandpass filter. In FIG. 3, the horizontal axis represents the full width at half maximum of the wavelength tunable optical bandpass filter, and the vertical axis represents the reception sensitivity penalty for realizing an error rate of 10 ⁻⁹ (degradation from reception sensitivity at a full width at half maximum of 0.3 nm). Are plotted). The transmission rate is 10 Gbps. As shown in FIG. 3, it can be seen that the reception sensitivity penalty rapidly deteriorates to a full width at half maximum of about 5 nm, and the slope is changed and the penalty increases gradually. It is understood that the full width at half maximum needs to be 5 nm or less when the deterioration of about 3 dB is allowed. In the case of the 1550 nm band, 1 nm corresponds to 125 GHz.

(Embodiment 2)
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 shows a wavelength multiplexing communication system having a redundant configuration by wavelength switching. The wavelength division multiplexing communication system 10 includes two optical transmission devices 30 and 30 ′, optical fibers 450-1 and 450-2 that transmit optical signals from the optical transmission devices 30 and 30 ′, and an optical fiber 450-1. And an optical receiver 400 that receives an optical signal input via 450-2.

Optical transmitter 30 includes a plurality of optical transmitters 140-1, 140-2 ... for transmitting the frequency _{f 1,} f 2 _... optical signals of frequency _f 1 to be transmitted from a plurality of optical transmitters, _{f 2} And an optical multiplexer 141 that multiplexes the optical signals and outputs a wavelength multiplexed signal to the optical fiber 450-1.

The optical transmitter 30 ′ transmits, for example, an optical signal of f ₁ + Δf (or f ₁ −Δf) shifted by Δf from the frequency of the optical signal transmitted from each of the optical transmitters 140-1, 140-2,. The optical signals transmitted from the plurality of optical transmitters 140′-1, 140′-2,... And the plurality of optical transmitters 140′-1, 140′-2,. And an optical multiplexer 141 ′ for outputting a multiplexed signal.

  The optical receiver 400 includes an optical demultiplexer 460 connected to the optical fibers 450-1 and 450-2, and a plurality of wavelength-independent optical receivers 220-1, 220-2,. The optical demultiplexer 460 is a two-input arrayed waveguide grating (AWG), and a wavelength multiplexed signal input via the optical fibers 450-1 and 450-2 is sent to the same port due to the circulatory property of the AWG. Output. The wavelength-independent optical receivers 220-1, 220-2,... Have the same configuration as the wavelength-independent optical receiver 220-1 in the first embodiment described with reference to FIG.

A redundant configuration by wavelength switching will be briefly described. The optical demultiplexer 460 is a two-input arrayed waveguide grating (AWG), and the input port is connected to two optical fibers 450-1 and 450-2. Here, it is assumed that the optical fiber 450-1 is a working optical fiber and the optical fiber 450-2 is a standby optical fiber. When there is no abnormality in the working optical fiber, the wavelength division multiplexed signal is sent to only one of the working optical fibers 450-2 when the working optical fiber 450-1 is broken. The Here, the frequency of Δf is used so that signals having different wavelengths can be sent to the same output port to the active optical fiber 450-1 and the standby optical fiber 450-2 by utilizing the circulatory property of the AWG in the optical demultiplexer 460. A wavelength-multiplexed signal with a shifted is transmitted. For example, if the frequency of the optical signal of a certain channel in the working optical fiber 450-1 and _{f 1,} the frequency of the optical signal of the channel corresponding thereto in the preliminary optical fiber 450-2 is _{f 1} + _Δf (or _{f 1} - Δf). Either one of these two signals is wavelength multiplexed and transmitted.

Here, a feature of the present invention is that the frequency of the center wavelength of the tunable optical bandpass filter 222 is set in advance to f ₁ + Δf / 2 (or f ₁ −Δf / 2). As a result, even when the wavelength changes due to wavelength switching in the relay section, there is no need to change the center wavelength of the wavelength tunable optical bandpass filter 222, and high-speed recovery (several tens of ms) can be realized when a failure occurs. It becomes possible. The full width at half maximum of the transmission wavelength in the wavelength tunable optical bandpass filter 222 is set to Δf or more, and it is necessary to set the transmission width to be sufficient to detect both of the two signals without changing the transmission center wavelength.

Use a tunable optical bandpass filter with a narrow full width at half maximum when high-speed switching is not required or when it is desired that strong optical power is not incident upon wavelength switching so as not to destroy the optical receiver 223. be able to. In this case, the frequency of the center wavelength f ₁ if the optical communication system 10 is operating in the working optical fiber 450-1, when it is operated in the standby optical fiber 450-2 is the center wavelength It is necessary to set the frequency to f ₁ + Δf (or f ₁ −Δf). An optical signal having a wavelength (frequency f ₁ ) transmitted through the active optical fiber 450-1 or an optical signal having a wavelength (frequency f ₁ + Δf (or f ₁ −Δf)) transmitted through the standby optical fiber 450-2. Only one of them can be transmitted.

  The optical communication system according to the present embodiment may be applied not only to a relay system but also to an access system having a redundant configuration.

  FIG. 5 shows an example of an initial setting algorithm of the transmission wavelength of the wavelength tunable optical bandpass filter 222.

  The output of the single channel optical amplifier is set to OFF (step 501), and the transmission wavelength of the wavelength tunable optical bandpass filter 222 is set to an initial value (step 502).

  Next, it is determined in the monitoring circuit 232 whether the input signal power is detected based on the output of the photodiode 227 (step 503). If the input signal power is not detected, an alarm indicating that the input signal is disconnected is issued (step 504). If the input signal power is detected, the process proceeds to step 505, where the output of the single channel optical amplifier is set to ON.

  Next, the monitoring circuit 232 determines whether the optical output power of the single-channel optical amplifier exceeds the lower limit based on the output of the photodiode 229 (step 506). If the optical output power does not exceed the lower limit, A single channel optical amplifier abnormality alarm is issued (step 507). When the optical output power exceeds the lower limit value, the wavelength control circuit 225 sweeps the transmission wavelength of the tunable optical bandpass filter 222 while monitoring the optical output power based on the output of the photodiode 231 (step 508). It is determined whether the optical output power exceeds the upper limit during the sweep (step 509). When the optical output power exceeds the upper limit value, the sweeping is stopped, the output power of the single channel optical amplifier is lowered in the constant output power control circuit (step 510), and the process returns to step 502. If the optical output power does not exceed the upper limit value, it is determined whether the sweep has been completed for all wavelength regions (step 511). Steps 508 to 511 are repeated until the sweep of the entire wavelength region is completed.

  When the sweep of the entire wavelength region is completed, it is then determined whether the wavelength control circuit 225 has detected the transmission wavelength of the wavelength tunable optical bandpass filter 222 that maximizes the transmitted light power (step 512). If the transmission wavelength at which the transmitted light power is maximized is not detected, an alarm for abnormality of the wavelength tunable optical bandpass filter 222 is issued (step 513). When the wavelength control circuit 225 detects the transmission wavelength at which the transmitted light power is maximum, the frequency fmax at which the detected transmitted light power is maximum, or the frequency shifted by fmax ± Δf / 2, is used as the wavelength variable optical bandpass filter. The transmission wavelength is set to 222 (step 514).

  Further, the wavelength control circuit 225 determines whether or not the transmitted light power is within a predetermined light level based on the output of the photodiode 231 (step 515), and the transmitted light power is not within the predetermined light level. In this case, the output power of the single-channel optical amplifier is adjusted in the constant output power control circuit 224 (step 516).

  In normal operation, it is also desirable from the viewpoint of system design that the wavelength control circuit 225 always monitors the transmitted light power and sets the wavelength tunable optical bandpass filter to follow the wavelength variation due to the aging of the LD. it is conceivable that. Various methods can be adopted as the realizing method and are not particularly defined in the present invention.

1 is a configuration diagram of a conventional wavelength division multiplexing communication system 10. FIG. It is a block diagram of the wavelength division multiplexing communication system which concerns on embodiment of this invention. It is a simulation result and an experimental result about the filter width of the wavelength variable optical bandpass filter of the wavelength independent optical receiver which concerns on embodiment of this invention. It is a block diagram of the wavelength division multiplexing communication system which concerns on embodiment of this invention. It is a flowchart which shows the initialization algorithm of the transmission wavelength of the wavelength variable optical band pass filter which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Wavelength multiplexing communication system 20,200,400 Optical receiver 30 Optical transmitter 100 Gain flattening WDM front optical amplifier 101 Constant gain control circuit 102 Optical fiber amplifier 103 Gain equalizer 104 Variable optical attenuator 105 Constant optical output power Control circuit 106, 108, 226, 228, 230 Optical coupler 107, 109, 227, 229, 231 Photo diode 110, 232 Monitoring circuit 120, 210, 460 Optical demultiplexer 130-1, 130-2, 223 Optical receiver 140-1, 140-2, 240-1, 240-2 Optical transmitter 141, 241 Optical multiplexer 150, 450-1, 450-2 Optical fiber 220, 220-1, 220-2 Wavelength independent optical receiver 221 Optical amplifier 222 Wavelength variable optical bandpass filter 224 Optical output power constant control circuit 225 Wavelength control circuit

Claims (9)

An optical receiver connected to an optical transmitter via an optical fiber,
A wavelength-demultiplexed optical demultiplexer that demultiplexes a wavelength-division-multiplexed optical signal in which one or a plurality of optical signals having non-overlapping wavelengths is wavelength-multiplexed into one or a plurality of the optical signals for each wavelength;
An optical amplifier that amplifies one of the optical signals demultiplexed by the optical demultiplexer to a desired optical power, an optical bandpass filter that transmits the optical signal amplified by the optical amplification means, And an optical receiver having an optical receiver for receiving the optical signal transmitted through the optical bandpass filter.   The optical receiver according to claim 1, wherein the optical bandpass filter is a wavelength tunable optical bandpass filter.   3. The optical receiver according to claim 2, wherein the tunable optical bandpass filter has a full width at half maximum of a transmission wavelength of 5 nm or less. The optical demultiplexer is an arrayed waveguide grating having a first input and a second input, the frequency multiplexed optical signal input to the first input and the second input to the second input. Demultiplexing the optical signals of frequency f ₀ and f ₀ ± Δf from the frequency multiplexed optical signals of
The frequency of the central wavelength of the transmission wavelength in the optical bandpass filter is f ₀ ± Δf / 2, and the full width at half maximum of the transmission wavelength is equal to or greater than Δf. Optical receiver. An optical communication system comprising an optical transmitter, an optical fiber, and an optical receiver,
The optical transmission device combines one or a plurality of optical transmitters that transmit optical signals having non-overlapping frequencies, and the optical signals from the optical transmitters, and enters the wavelength-multiplexed optical signal into the optical fiber. Equipped with an optical multiplexer,
The optical receiver is an optical demultiplexer that demultiplexes the wavelength-multiplexed optical signal input through the optical fiber into one or more optical signals for each frequency, and is demultiplexed by the optical demultiplexer. An optical amplifier that amplifies one of the optical signals to a desired optical power, an optical bandpass filter that transmits the optical signal amplified by the optical amplifier, and transmitted through the optical bandpass filter An optical communication system comprising: one or a plurality of optical receivers having an optical receiver for receiving the optical signal. An optical communication system in which a first optical transmitter and a second optical transmitter are connected to an optical receiver via a first optical fiber and a second optical fiber, respectively.
The first optical transmission device combines one or a plurality of first optical transmitters that transmit optical signals having non-overlapping frequencies, and optical signals from the first transmitter to combine the first wavelength multiplexed light. A first optical multiplexer for injecting a signal into the first optical fiber;
The second optical transmitter includes one or a plurality of second optical transmitters that respectively transmit optical signals having a frequency shifted by Δf from the frequency of the optical signal transmitted by each of the first optical transmitters; A second optical multiplexer that multiplexes the optical signals from the transmitter and enters the second wavelength-multiplexed optical signal into the second optical fiber,
The optical receiver is
An arrayed waveguide grating having a first input and a second input, the first frequency multiplexed optical signal input to the first input and the second frequency multiplexed optical signal input to the second input, An optical demultiplexer for demultiplexing optical signals of frequencies f ₀ and f ₀ ± Δf and outputting them to the same port;
An optical amplifier that amplifies one of the optical signals demultiplexed by the optical demultiplexer, an optical bandpass filter that transmits the optical signal amplified by the optical amplification means, and the optical bandpass An optical communication system comprising: one or a plurality of optical receivers having an optical receiver for receiving the optical signal that has passed through the filter.   The optical communication system according to claim 5 or 6, wherein the optical bandpass filter is a wavelength tunable optical bandpass filter.   8. The optical communication system according to claim 7, wherein the tunable optical bandpass filter has a full width at half maximum of a transmission wavelength of 5 nm or less. 9. The optical communication according to claim 7, wherein a frequency of a central wavelength of the transmission wavelength in the wavelength tunable optical bandpass filter is f ₀ ± Δf / 2, and a full width at half maximum of transmission is Δf or more. system.

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