JP2013074439A - Optical communication system, optical communication method, optical transmitter-cum- receiver, optical transmitter, optical receiver, and method for controlling them - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform more reliable channel multiplex communication by eliminating a configuration for modulation and integration to identify a channel at a transmission side and a configuration for demodulation and separation at a reception side.SOLUTION: An optical transmitter comprises: a first light source for emitting continuous light with a changeable wavelength; and a first wavelength changing unit for changing the wavelength of light emitted by the first light source at a first change frequency specific to an allocated transmission channel. An optical receiver receiving an optical signal from the optical transmitter comprises: a frequency detection unit for detecting a second change frequency from a wavelength change compared with the wavelength of light emitted by the first light source on the basis of the received optical signal; and a channel identification unit for confirming reception of the optical signal from a desired reception channel if the detected second change frequency accords with the first change frequency specific to the allocated transmission channel.

Description

  The present invention relates to a channel multiplexing technique in an optical communication system.

  In the above technical field, as shown in Patent Document 1, the relationship between temperature, applied current and oscillation wavelength is stored in advance, and the oscillation light wavelength of the local oscillation light source for receiving optical signals and the transmission light source is controlled. The technology to do is known. In Patent Document 1, the pilot signal superimposed on the optical signal of each channel is extracted by minutely changing the wavelength of the local oscillation light source. Then, it is confirmed from the pilot signal whether the reception channel is desired. Patent Document 2 describes a technique for creating a wavelength sweep light source using an applied current, a phase modulator, an external resonator, or a pulse light source and a dispersion medium. And in patent document 2, this one wavelength sweep light source is shared by the several channel which should be multiplexed, and channel multiplexing is implement | achieved.

Japanese Patent Laid-Open No. 04-212530 JP 2010-148007 A

  However, the technique described in Patent Document 1 is a technique for superimposing a pilot signal separately from data for optical communication, and the technique described in Patent Document 2 is only a technique for creating a channel frequency with one wavelength sweep light source. Absent. That is, the wavelength fluctuation itself of the transmission light source itself is not used as information for confirming whether the channel is a desired reception channel.

  The objective of this invention is providing the technique which solves the above-mentioned subject.

In order to achieve the above object, a system according to the present invention provides:
An optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
The optical transmitter
A first light source that emits continuous light having a variable wavelength;
First wavelength changing means for changing a wavelength of light emitted from the first light source at a first changed frequency specific to an assigned transmission channel;
With
An optical receiver that receives an optical signal from the optical transmitter,
Frequency detecting means for detecting a second changed frequency from a change in wavelength based on the wavelength of the light emitted from the first light source based on the received optical signal;
Channel identification means for confirming that an optical signal has been received from a desired receiving channel when the detected second changed frequency matches the first changed frequency specific to the assigned transmission channel;
It is characterized by providing.

In order to achieve the above object, the method according to the present invention comprises:
An optical communication method of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
A wavelength changing step in which the optical transmitter changes the wavelength of the continuous light emitted by the first light source at a first changed frequency specific to the assigned transmission channel;
A frequency detection step in which the optical receiver detects a second change frequency from a change in wavelength based on the wavelength of the light emitted from the first light source, based on the received optical signal;
A channel identification step for confirming that the optical receiver has received an optical signal from a desired reception channel when the detected second modified frequency matches the first modified frequency specific to the assigned transmission channel; When,
It is characterized by including.

In order to achieve the above object, an apparatus according to the present invention provides:
The optical transmitter of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
A first light source that emits continuous light having a variable wavelength;
Wavelength changing means for changing the wavelength of the light emitted by the first light source at a first changing frequency specific to the assigned transmission channel;
It is characterized by providing.

In order to achieve the above object, the method according to the present invention comprises:
A method of controlling the optical transmitter of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
The method includes a wavelength changing step of changing a wavelength of continuous light emitted from the first light source at a first changing frequency specific to the assigned transmission channel.

In order to achieve the above object, an apparatus according to the present invention provides:
The optical receiver of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
Frequency detecting means for detecting a second changed frequency from a change in wavelength based on the wavelength of light emitted from the first light source of the optical transmitter based on the received optical signal;
The detected second change frequency is a first change frequency specific to a transmission channel assigned to the optical transmitter, and the optical transmitter changes the wavelength of light emitted from the first light source. Channel identification means for confirming that an optical signal has been received from a desired reception channel when the first change frequency used is matched;
It is characterized by providing.

In order to achieve the above object, the method according to the present invention comprises:
A method for controlling the optical receiver of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
A frequency detecting step of detecting a second changed frequency from a change in wavelength based on the wavelength of light emitted from the first light source of the optical transmitter based on the received optical signal;
The detected second change frequency is a first change frequency specific to a transmission channel assigned to the optical transmitter, and the optical transmitter changes the wavelength of light emitted from the first light source. A channel identification step for confirming that an optical signal is received from a desired reception channel when the first change frequency used is matched;
It is characterized by including.

In order to achieve the above object, an apparatus according to the present invention provides:
An optical transceiver for transmitting and receiving optical signals,
A light source that emits continuous light whose wavelength can be changed;
Wavelength changing means for changing the wavelength of light emitted by the light source at a first changing frequency specific to the assigned transmission channel;
Frequency detecting means for detecting a second changed frequency from a change in wavelength based on the wavelength of the light emitted from the light source of the transmission source based on the received optical signal;
The detected second change frequency is a third change frequency specific to a transmission channel assigned to the transmission source, and is used to change the wavelength of light emitted from the light source of the transmission source at the transmission source. Channel identification means for confirming that an optical signal has been received from a desired reception channel when the third changed frequency matches,
It is characterized by providing.

In order to achieve the above object, the method according to the present invention comprises:
An optical transceiver control method for transmitting and receiving an optical signal,
A wavelength changing step for changing a wavelength of continuous light emitted by the light source at a first changing frequency specific to the assigned transmission channel;
A frequency detection step of detecting a second changed frequency from a change in wavelength based on the wavelength of the light emitted from the light source of the transmission source based on the received optical signal;
The detected second change frequency is a third change frequency specific to a transmission channel assigned to the transmission source, and is used to change the wavelength of light emitted from the light source of the transmission source at the transmission source. A channel identifying step for confirming that an optical signal has been received from a desired receiving channel when the third changed frequency matches,
It is characterized by including.

  According to the present invention, since the wavelength variation of the transmission light source itself is used as information for confirming whether the channel is a desired reception channel, the configuration on the transmission side for channel identification or the composition for synthesis and the demodulation on the reception side In addition, a more reliable channel multiplex communication can be performed without the configuration for separation.

1 is a block diagram showing a configuration of an optical communication system according to a first embodiment of the present invention. It is a block diagram which shows the structure of the optical communication system which concerns on 2nd Embodiment of this invention. It is a figure which shows the concept of the optical communication method which concerns on 2nd Embodiment of this invention. It is a figure which shows the structure of the whole light source of the coherent optical transmitter which concerns on 2nd Embodiment of this invention. It is a figure which shows the structure of the channel identification part of the coherent optical receiver which concerns on 2nd Embodiment of this invention. It is a flowchart which shows the process sequence of the coherent optical receiver which concerns on 2nd Embodiment of this invention. It is a block diagram which shows the structure of the optical communication system which concerns on 3rd Embodiment of this invention. It is a figure which shows the structure of the whole local light source of the coherent optical receiver which concerns on 3rd Embodiment of this invention. It is a figure which shows the structure of the whole light source of the coherent optical transmitter which concerns on 4th Embodiment of this invention. It is a figure which shows the structure of the channel identification part of the coherent optical receiver which concerns on 4th Embodiment of this invention.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the constituent elements described in the following embodiments are merely examples, and are not intended to limit the technical scope of the present invention only to them.

[First Embodiment]
An optical communication system 100 as a first embodiment of the present invention will be described with reference to FIG. The optical communication system 100 is a system in which an optical transmitter 110 and an optical receiver 120 are connected by an optical transmission line 130.

  As shown in FIG. 1, in an optical communication system 100, an optical transmitter 110 includes a first light source 111 and a first wavelength changing unit 112, an optical receiver 120 includes a frequency detection unit 121, and a channel identification. Part 122. The first light source 111 emits continuous light whose wavelength λ can be changed. The first wavelength changing unit 112 changes the wavelength λx of the light emitted from the first light source 111 at the first changed frequency fx1 specific to the assigned transmission channel. Based on the received optical signal, the frequency detector 121 detects the second changed frequency fx2 from the change in wavelength with the wavelength λx of the light emitted from the first light source 111 as a reference. When the detected second change frequency λx2 matches the first change frequency λx1 specific to the assigned transmission channel, the channel identification unit 122 confirms that the optical signal has been received from the desired reception channel.

  According to this embodiment, since the wavelength variation of the transmission light source itself is used as information for identifying whether the channel is a desired reception channel, the configuration for modulation and synthesis on the transmission side for channel identification and the reception side Channel multiplex communication without the configuration for demodulating and separating the signal.

[Second Embodiment]
Next, an optical communication system 200 according to the second embodiment of the present invention will be described. In this embodiment, in coherent optical communication, the wavelength of a laser diode light source (hereinafter referred to as an LD (Laser Diode) light source) on the transmitter side is minutely varied at a frequency peculiar to each channel. Channel identification is performed by detecting a frequency specific to each channel. The frequency peculiar to each channel used here is several tens KHz, which is smaller than the frequency of the data input signal to be transmitted.

  According to the present embodiment, the configuration for modulation and synthesis on the transmission side for channel identification and the configuration for demodulation and separation on the reception side are eliminated, and channel multiplex communication with more reliable channel identification can be performed. .

<< Configuration of optical communication system >>
FIG. 2 is a block diagram showing the configuration of the optical communication system 200 according to the present embodiment.

  The optical communication system 200 that is the coherent optical communication system illustrated in FIG. 2 is a system in which a plurality of coherent optical transmitters 210 and a plurality of coherent optical receivers 220 are connected through an optical transmission line 230. In an actual optical communication system, a repeater, an amplifier, an optical branching device, an optical distributor, and the like are arranged, but are omitted because they are not characteristic portions of this embodiment. In FIG. 2, the description will be given focusing on one coherent optical transmitter 210 and one coherent optical receiver 220.

(Coherent optical transmitter)
The coherent optical transmitter 210 in FIG. 2 includes an LD light source 211, an oscillator 212, an LN (lithium niobate) optical modulator 213, and a drive amplifier 214. The LD light source 211, which is a semiconductor laser, generates laser light by, for example, totally reflecting photons generated in an active layer between clad layers having a double hetero structure on a cleavage plane (see FIG. 4). The wavelength of the LD light source 211 can be changed according to the distance between the semiconductor material and the cleavage plane, and is set to 1260 nm to 1625 nm which is a wavelength band used in optical communication.

  In this embodiment, the wavelength of the LD light source 211 is minutely changed by applying a current to the LD light source 211 from the oscillator 212 at a predetermined frequency (in this example, several tens of KHz). The oscillation frequency of the oscillator is predetermined for each channel for transmitting an optical signal. For example, 10 kHz is set for λ1, 20 kHz for λ2,..., Λn is set to nKHz. The change width of the wavelength is a range that does not affect the sensitivity characteristic and the signal quality characteristic in the coherent optical receiver 220 as compared with, for example, 1260 nm to 1625 nm which is a wavelength band of optical communication. Specifically, the change width of the wavelength is preferably several percent (less than 5 to 10%) of the fundamental wavelength λx of the LD light source 211. As a method for minutely changing the wavelength of the LD light source 211, a method using heat is also conceivable, but it is desirable to apply a current with a high change rate and no delay.

  The laser light 211a from the LD light source 211 that slightly fluctuates at a predetermined frequency predetermined for each channel from a predetermined wavelength is modulated by a data input signal 215 to be transmitted amplified by a drive amplifier 214 by an LN optical modulator 213. Is done. As described above, in this embodiment, the optical signal output output from the LN optical modulator 213 to the optical transmission line 230 is ± Δλ fluctuation when the intrinsic optical wavelength λx of the channel x in the LD light source 211 is the frequency fx1 of the oscillator 212. The laser beam 211a is modulated by a data input signal 215 to be transmitted. That is, as shown in FIG. 2, the optical signal output uses λx ± Δλ as the carrier laser beam.

  Here, the optical signal spectrum transmitted from the coherent optical transmitter 210 becomes an optical spectrum (no change) 241 when there is no minute change in wavelength by the oscillator 212 (zero). Further, when a minute change to the wavelength is performed, an optical spectrum (changed at fxHz) 242 is obtained. An optical spectrum (WDM: Wavelength Division Multiplexing) 240 obtained by combining these optical signals with a plurality of channels is sent out to the optical transmission line 230. Here, each of A to H is an optical spectrum of the LD light source 211 that is the basis of each channel, and in this embodiment, this wavelength λx (x = A to H) is changed by ± Δλ at a channel-specific frequency. I will let you.

(Coherent optical receiver)
The coherent optical receiver 220 includes a front end unit 221, an ADC / DSP (Analog Digital Converter / Digital Signal Processor) 222, a local light source (hereinafter referred to as LO: Local Oscillator) 223, an LD light source change frequency detection unit 224, And a channel identification unit 225. The front end unit 221 performs coherent detection of the received optical signal. The ADC / DSP 222 performs signal processing of the detected optical signal and demodulation of the data signal. Then, the data output 226 transmitted by the laser beam having the wavelength λx is obtained. The local light source (LO) 223 generates laser light having the same wavelength as that of the LD light source 211 in order to cause interference of the laser light transmitted through the optical transmission path 230. The LD light source change frequency detector 224 detects the frequency of the signal oscillated by the oscillator 212 from the fluctuation of the optical wavelength in the received signal (± Δλ, also referred to as “fluctuation”). The channel identification unit 225 is a channel in which the channel of the received optical signal is desired from the frequency fx2224a detected by the LD light source change frequency detection unit 224 and the optical wavelength λx223a set in the local light source (LO) 223. Identify if there is any. That is, if the carrier laser light having the same optical wavelength λx and the frequency fx2 of the wavelength fluctuation detected from the carrier laser light coincides with the frequency fx1 swayed in the LD light source 211 on the transmission side, the current detection / demodulation It is recognized that the data output 226 is the data of the desired channel. Then, the identification result is output as a channel identification signal 227.

《Concept of optical communication method》
FIG. 3 is a diagram illustrating a concept of the optical communication method 300 according to the present embodiment. FIG. 3 particularly shows the wavelength λx when the wavelength λx of the laser light generated from the LD light source 211 is 1260 nm to 1625 nm, which is the wavelength band of optical communication, and the frequency at which the wavelength is slightly shaken for channel identification. The relationship with fx1 is shown.

  The waveform (a) in FIG. 3 is a waveform of the wavelength λx without a minute fluctuation in the wavelength. The wavelength is between 1260 nm and 1625 nm, and is between 239 THz and 185 THz in terms of frequency.

On the other hand, the waveform (b) in FIG. 3 is a waveform of the frequency fx1 that causes the wavelength to slightly fluctuate. The frequency fx1 is several tens KHz. For example, in the case of 10 KHz, the wavelength is 3 × 10 ¹³ nm. Therefore, the waveform (b) in FIG. 3 does not accurately represent the dimensional ratio with the waveform (a) in FIG.

  The waveform (c) in FIG. 3 is a waveform obtained by slightly shifting the wavelength λx by the frequency fx1 (± Δλ). In the present embodiment, the LN optical modulator 213 modulates the laser beam having the waveform (c) with the data input signal 215 to be transmitted, and outputs it to the optical transmission line 230.

(Light source of coherent optical transmitter)
FIG. 4 is a diagram illustrating a configuration of the entire light source of the coherent optical transmitter 210 according to the present embodiment. Although FIG. 4 shows an example in which an LD light source is used as the light source, the present invention is not limited to this.

  As shown in the figure, the LD light source 211 has a double hetero structure in which an n-type cladding layer, an active layer, and a p-type cladding layer are stacked on an n-type substrate. Electric power is applied between the electrodes from the power source 413, and light is emitted by an energy gap in the active layer. The light fills up by being totally reflected by the cleaved surface (left and right surfaces in FIG. 4) and the boundary surface between the cladding layers in the active layer, and emits light as laser light from one of the cleaved surfaces.

  In this embodiment, the oscillator 212 causes the voltage V (λx) applied between the electrodes of the LD light source to be minutely ± ΔV (± Δλ) at the frequency fx1. That is, the voltage applied between the electrodes of the LD light source is a voltage V (λx) of the power source 413 adjusted to generate laser light of wavelength λx, and a minute voltage ± ΔV (± Δλ) at the frequency fx1 of the oscillator 212. The voltage increases or decreases {V (λx) ± ΔV (± Δλ)}. When the current value changes approximately in proportion to the change in the voltage applied between the electrodes of the LD light source, the refractive index of the active layer of the LD light source 211 changes slightly at the frequency fx1, and the oscillation wavelength of the laser light varies. To do. As a result, as shown in the waveform (c) of FIG. 3, a laser beam 211a having a frequency of ± Δλ with respect to the wavelength λx having a frequency specific to the channel is emitted. The laser light 211a is modulated by the data input signal 215 to be transmitted by the LN optical modulator 213 and output as an optical signal output. In the lower right of FIG. 4, a schematic diagram of the time change of the voltage applied to the LD light source 211 is shown.

  In FIG. 4, a power source 413 that outputs a voltage V (λx) to generate laser light having a wavelength λx and a minute voltage ± ΔV (± Δλ) are output to vary the oscillation wavelength by ± Δλ at the frequency fx1. Each oscillator 212 is provided, but one variable voltage supply unit capable of outputting a voltage {V (λx) ± ΔV (± Δλ)} may be provided.

(Channel identification part of coherent optical receiver)
FIG. 5 is a diagram illustrating a configuration of the channel identification unit 225 of the coherent optical receiver 220 according to the present embodiment.

  The channel identification unit 225 includes a wavelength / frequency comparison unit 510 and a wavelength / frequency storage unit 520. The wavelength / frequency storage unit 520 stores an LD light source wavelength λx521 that outputs an optical signal to a desired channel, and an oscillator change frequency fx1522 that oscillates the wavelength of the LD light source that outputs an optical signal to the desired channel. .

  The wavelength / frequency comparison unit 510 compares the local light source wavelength λx acquired from the local light source (LO) 223 with the LD light source wavelength λx 521 stored in the wavelength / frequency storage unit 520. Further, the wavelength / frequency comparison unit 510 compares the detection change frequency fx2 acquired from the LD light source change frequency detection unit 224 with the change frequency fx1 stored in the wavelength / frequency storage unit 520. If the light source wavelengths and the changed frequencies match, the channel identifying unit 225 identifies that the channel currently demodulating the data output 226 is the desired channel. Then, a channel identification signal 227 is output.

<Processing procedure of coherent optical receiver>
FIG. 6 is a flowchart showing a processing procedure of the coherent optical receiver 220 according to the present embodiment. This flowchart is executed by a CPU that controls the coherent optical receiver 220, thereby controlling each functional element in FIG. 2 or realizing a part thereof.

  First, in step S601, the change frequency fx2 of the transmission side LD light source is detected from the received optical signal. Next, in step S603, wavelength information is acquired from the local light source (LO). In step S605, it is determined whether or not the acquired wavelength and the changed frequency match the wavelength λx and the frequency fx1 stored in the wavelength / frequency storage unit 520. If they match, the process proceeds to step S607 to output a channel identification signal 227. On the other hand, if they do not match, the process ends without outputting the channel identification signal 227. That is, the data output 226 is determined not to be data of a desired channel.

[Third Embodiment]
Next, an optical communication system according to a third embodiment of the present invention will be described. Compared with the second embodiment, the optical communication system according to the present embodiment includes an oscillator that synchronizes the wavelength of the LO light source with the LD light source of the coherent optical transmitter with a minute fluctuation of the wavelength compared to the second embodiment. Is different. Since other configurations and operations are the same as those of the second embodiment, the same configurations and operations are denoted by the same reference numerals, and detailed description thereof is omitted.

  According to the present embodiment, it is possible to suppress an adverse effect on transmission / reception data due to a minute fluctuation of the wavelength of the LD light source of the coherent optical transmitter.

<< Configuration of optical communication system >>
FIG. 7 is a block diagram showing a configuration of an optical communication system 700 according to the present embodiment. The configuration of the optical communication system 700, which is a coherent optical communication system, is different from the optical communication system 200 of the second embodiment in that the coherent optical receiver 720 includes an oscillator 726, but the coherent optical transmitter 210 and The optical transmission line 230 is the same. Therefore, the same configurations and operations as those of the second embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the configuration of FIG. 2 of the second embodiment, the optical wavelength of the optical signal is varied in the coherent optical transmitter 210 even though it is very small, and this has a considerable influence on the demodulation of the signal in the coherent optical receiver 220. In order to alleviate this, in the present embodiment, the following operation is performed in the coherent optical receiver 720.

  In the coherent optical receiver 720, the local light source (LO) 723 emits the same optical wavelength as the optical signal λx of the channel to be selected, and the front-end unit 221 performs coherent detection of the optical reception signal. This detection signal is demodulated after signal processing by the ADC / DSP 222 of the next stage and outputs a data output 226. In the signal processing process in the ADC / DSP 222, a minute shake (± Δλ) of the carrier laser light emitted from the LD light source is detected and sent to the LD light source change frequency detector 224. The LD light source change frequency detection unit 224 detects a minute vibration frequency fx 2 and sends the result to the channel identification unit 225. The operation so far is the same as in the second embodiment.

  In the present embodiment, the LD light source change frequency detection unit 224 sends the minute shake change frequency fx2 to the channel identification unit 225 and simultaneously synchronizes with the oscillation frequency of the oscillator 726. The oscillation frequency fx2 of the oscillator 726 matches the frequency fx1 of the oscillator 212 that oscillates the wavelength of the LD light source 211 on the transmission side when data of a desired channel is acquired. At the oscillation frequency fx2 of the oscillator 726, the light wavelength λx of the laser light 723a emitted from the local light source (LO) 723 is slightly changed.

  In general, the difference between the optical wavelength of the carrier laser light emitted from the LD light source 211 and the laser light emitted from the local light source (LO) 723 is large, and the fact that it swings at high speed is Affects processing and demodulation. The light wavelength of the local light source (LO) 723 is swung in synchronization with the vibration of the LD light source 211 by the oscillation output of the oscillator 726. As described above, if the optical wavelength difference with the carrier laser beam is set to be relaxed, it is possible to reduce the influence on the sensitivity characteristic and the signal quality characteristic in the coherent optical receiver 720.

  Actually, if the optical wavelength difference between the carrier laser beam and the local light source (LO) 723 is controlled to be small, it becomes difficult to detect the vibration frequency by the LD light source change frequency detector 224. Therefore, during the first period when the coherent optical receiver 720 is started, the operation of the oscillator 726 is stopped, and the detection of the vibration frequency in the LD light source change frequency detector 224 is facilitated. Thereafter, after the determination by the channel identification unit 225 is made, the oscillator 726 may be operated to reduce the influence on the processing and demodulation in the ADC / DSP 222.

(Local light source of coherent optical receiver)
FIG. 8 is a diagram illustrating a configuration of the entire local light source of the coherent optical receiver 720 according to the present embodiment. Although FIG. 8 shows an example in which an LD light source is used as the local light source, the present invention is not limited to this.

  As shown in the drawing, the local light source (LO) 723 has a double hetero structure in which an n-type cladding layer, an active layer, and a p-type cladding layer are stacked on an n-type substrate. Electric power is applied between the electrodes from a power source 724, and light is emitted by an energy gap in the active layer. The light fills up by being totally reflected by the cleaved surface (left and right surfaces in FIG. 7) and the boundary surface between the cladding layers in the active layer, and emits light as laser light from one of the cleaved surfaces.

  In the present embodiment, the LD light source change frequency detection unit 224 notifies the oscillator 726 of the detected frequency fx2 of fluctuation to the wavelength λx in the LD light source 211. By applying a minute voltage of frequency fx2 to the local light source (LO) 723 by the oscillator 726, a laser beam 723a having a frequency characteristic of the channel with a fluctuation of ± Δλ with respect to the wavelength λx is emitted. This laser beam 723a interferes with the received optical signal and is more accurately coherently detected by the front end unit 221. Further, the local light source (LO) 723 notifies the channel identification unit 225 of the wavelength λx for channel identification.

[Fourth Embodiment]
Next, an optical communication system according to a fourth embodiment of the present invention will be described. The optical communication system according to this embodiment is different from the second embodiment and the third embodiment in that the LD light source of the coherent optical transmitter and the channel identifier of the coherent optical receiver have the light source wavelength and The difference is that the set with the frequency of wavelength change for channel identification is changed. Since other configurations and operations are the same as those of the second embodiment or the third embodiment, the same configurations and operations are denoted by the same reference numerals, and detailed description thereof is omitted.

  According to the present embodiment, even when a channel is dynamically allocated to a coherent optical transmitter and a coherent optical receiver, the configuration and the receiving side for modulation and synthesis on the transmission side for channel identification Channel multiplex communication without a configuration for demodulation and separation in the network can be performed.

(Light source of coherent optical transmitter)
FIG. 9 is a diagram illustrating a configuration of the entire light source of the coherent optical transmitter 900 according to the present embodiment. Although FIG. 9 shows an example in which an LD light source is used as the light source, the present invention is not limited to this.

  As shown in the drawing, the LD light source 911 has a double hetero structure in which an n-type cladding layer, an active layer, and a p-type cladding layer are stacked on an n-type substrate. Power is applied from the power source 913 between the electrodes, and light is emitted by an energy gap in the active layer. The light is filled in the active layer by being totally reflected at the cleaved surface (left and right surfaces in FIG. 9) and the boundary surface between the cladding layers, and emits light as laser light from one of the cleaved surfaces.

  In this embodiment, first, the variable power source 913 applies a voltage that determines the wavelength λx to the LD light source 911, thereby setting the wavelength λx corresponding to the assigned channel. Next, by applying a current of frequency fx1 to the LD light source 911 by the oscillator 912, a laser light 911a having a frequency fx1 characteristic to the channel with a fluctuation of ± Δλ with respect to the wavelength λx is emitted.

  The voltage of the variable power source 913 and the frequency of the oscillator 912 are determined with reference to the wavelength / frequency storage table 920. The wavelength / frequency storage table 920 stores the LD light source wavelength λx922 and the changed frequency fx1923 in association with the assigned channel 921.

  The emitted laser beam 911a is modulated by a data input signal 215 to be transmitted in an LN optical modulator 213 (not shown in FIG. 9) and output as an optical signal output. A schematic diagram of the change over time of the voltage applied to the LD light source 911 is shown in the center right of FIG.

  In FIG. 9, a variable power source 913 that is adjusted to generate laser light having a wavelength λx and an oscillator 912 that varies the oscillation wavelength by ± Δλ at a frequency fx1 are provided. One variable voltage supply unit may be provided.

(Channel identification part of coherent optical receiver)
FIG. 10 is a diagram illustrating a configuration of the channel identification unit 1025 of the coherent optical receiver 1000 according to the present embodiment.

  The channel identification unit 1025 includes a wavelength / frequency comparison unit 1010 and a wavelength / frequency storage unit 1020. In the wavelength / frequency storage unit 1020, the LD light source wavelength λx1022 that outputs an optical signal to the assigned channel in association with the assigned channel 1021, and the wavelength of the LD light source that outputs the optical signal to the assigned channel are stored. The oscillator change frequency fx11023 for oscillation is stored. Which data stored in the wavelength / frequency storage unit 1020 is used is selected according to the assigned channel.

  The wavelength / frequency comparison unit 510 includes a local light source wavelength λx acquired from the local light source (LO) 223, an LD light source wavelength λx1011 corresponding to the allocated channel CHx acquired from the wavelength / frequency storage unit 1020, and Compare Further, the detection change frequency fx2 acquired from the LD light source change frequency detection unit 224 is compared with the change frequency fx1 corresponding to the allocated channel CHx acquired from the wavelength / frequency storage unit 1020. If both the light source wavelengths and the changed frequencies match, it is identified that the channel currently demodulating the data output 226 is an assigned channel. Then, a channel identification signal 227 is output.

[Other Embodiments]
In the above embodiment, the fluctuation of ± Δλ of the wavelength of the frequency Fx1 is generated by the minute fluctuation of the applied voltage, but the semiconductor refraction is also caused by the temperature change by heating / cooling separately from the applied voltage of the laser light emission of the wavelength λx. Since the rate changes, the oscillation wavelength can be changed minutely in the same manner.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. In addition, a system or an apparatus in which different features included in each embodiment are combined in any way is also included in the scope of the present invention.

  For example, in this embodiment, the optical transmitter and the optical receiver are illustrated independently in FIGS. 2 and 7, but each is an optical transceiver in which the optical transmitter and the optical receiver are integrated. It doesn't matter. In that case, in the optical transmitter / receiver at the transmission source, a carrier laser beam having a wavelength λx oscillated by ± Δλ at a frequency fx1 is emitted from the LD light source, and in the optical transmitter / receiver at the transmission destination, the LD light source change frequency detector Channel identification is performed by detecting fx2.

  In addition, the present invention may be applied to a system composed of a plurality of devices, or may be applied to a single device. Furthermore, the present invention can also be applied to a case where a control program that realizes the functions of the embodiments is supplied directly or remotely to a system or apparatus. Therefore, in order to realize the functions of the present invention on a computer, a control program installed in the computer, a medium storing the control program, and a WWW (World Wide Web) server that downloads the control program are also included in the scope of the present invention. include.

[Other expressions of embodiment]
A part or all of the above-described embodiment can be described as in the following supplementary notes, but is not limited thereto.
(Appendix 1)
An optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
The optical transmitter
A first light source that emits continuous light having a variable wavelength;
First wavelength changing means for changing a wavelength of light emitted from the first light source at a first changed frequency specific to an assigned transmission channel;
With
An optical receiver that receives an optical signal from the optical transmitter,
Frequency detecting means for detecting a second changed frequency from a change in wavelength based on the wavelength of the light emitted from the first light source based on the received optical signal;
Channel identification means for confirming that an optical signal has been received from a desired receiving channel when the detected second changed frequency matches the first changed frequency specific to the assigned transmission channel;
An optical communication system comprising:
(Appendix 2)
The optical receiver is
A second light source that emits continuous light whose wavelength can be changed, wherein the second light source emits light having the same wavelength as the light emitted by the first light source in order to cause interference with an optical reception signal;
Second wavelength changing means for changing a wavelength of light emitted from the second light source at the second changed frequency detected by the frequency detecting means;
Further comprising
The optical communication system according to appendix 1, wherein the frequency detection unit detects the second change frequency based on an optical reception signal interfered with continuous light emitted from the second light source.
(Appendix 3)
The optical communication according to appendix 1 or 2, wherein the first change frequency of the first wavelength changing means is on the order of several tens of KHz when the wavelength of the first light source is a wavelength band of optical communication. system.
(Appendix 4)
The change width of the wavelength of the first light source changed by the first wavelength changing means is 10% of the wavelength of the first light source in a range that does not affect the sensitivity characteristics and signal quality characteristics of the optical receiver. The optical communication system according to any one of appendices 1 to 3, wherein the optical communication system is less than or equal to 1.
(Appendix 5)
The optical communication system according to any one of appendices 2 to 4, wherein the first light source and the second light source include a semiconductor laser whose wavelength can be changed by applying a current.
(Appendix 6)
The optical communication system is a coherent optical communication system,
The optical communication system according to any one of appendices 1 to 5, wherein the optical transmitter is a coherent optical receiver, and the optical receiver is a coherent optical receiver.
(Appendix 7)
An optical communication method of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
A wavelength changing step in which the optical transmitter changes the wavelength of the continuous light emitted by the first light source at a first changed frequency specific to the assigned transmission channel;
A frequency detection step in which the optical receiver detects a second change frequency from a change in wavelength based on the wavelength of the light emitted from the first light source, based on the received optical signal;
A channel identification step for confirming that the optical receiver has received an optical signal from a desired reception channel when the detected second modified frequency matches the first modified frequency specific to the assigned transmission channel; When,
An optical communication method comprising:
(Appendix 8)
The optical transmitter of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
A first light source that emits continuous light having a variable wavelength;
Wavelength changing means for changing the wavelength of the light emitted by the first light source at a first changing frequency specific to the assigned transmission channel;
An optical transmitter comprising:
(Appendix 9)
A method of controlling the optical transmitter of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
A method for controlling an optical transmitter, comprising: a wavelength changing step of changing a wavelength of continuous light emitted from a first light source at a first changing frequency specific to an assigned transmission channel.
(Appendix 10)
The optical receiver of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
Frequency detecting means for detecting a second changed frequency from a change in wavelength based on the wavelength of light emitted from the first light source of the optical transmitter based on the received optical signal;
The detected second change frequency is a first change frequency specific to a transmission channel assigned to the optical transmitter, and the optical transmitter changes the wavelength of light emitted from the first light source. Channel identification means for confirming that an optical signal has been received from a desired reception channel when the first change frequency used is matched;
An optical receiver comprising:
(Appendix 11)
A method for controlling the optical receiver of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
A frequency detecting step of detecting a second changed frequency from a change in wavelength based on the wavelength of light emitted from the first light source of the optical transmitter based on the received optical signal;
The detected second change frequency is a first change frequency specific to a transmission channel assigned to the optical transmitter, and the optical transmitter changes the wavelength of light emitted from the first light source. A channel identification step for confirming that an optical signal is received from a desired reception channel when the first change frequency used is matched;
An optical receiver control method comprising:
(Appendix 12)
An optical transceiver for transmitting and receiving optical signals,
A light source that emits continuous light whose wavelength can be changed;
Wavelength changing means for changing the wavelength of light emitted by the light source at a first changing frequency specific to the assigned transmission channel;
Frequency detecting means for detecting a second changed frequency from a change in wavelength based on the wavelength of the light emitted from the light source of the transmission source based on the received optical signal;
The detected second change frequency is a third change frequency specific to a transmission channel assigned to the transmission source, and is used to change the wavelength of light emitted from the light source of the transmission source at the transmission source. Channel identification means for confirming that an optical signal has been received from a desired reception channel when the third changed frequency matches,
An optical transceiver characterized by comprising:
(Appendix 13)
An optical transceiver control method for transmitting and receiving an optical signal,
A wavelength changing step for changing a wavelength of continuous light emitted by the light source at a first changing frequency specific to the assigned transmission channel;
A frequency detection step of detecting a second changed frequency from a change in wavelength based on the wavelength of the light emitted from the light source of the transmission source based on the received optical signal;
The detected second change frequency is a third change frequency specific to a transmission channel assigned to the transmission source, and is used to change the wavelength of light emitted from the light source of the transmission source at the transmission source. A channel identifying step for confirming that an optical signal has been received from a desired receiving channel when the third changed frequency matches,
An optical transceiver control method comprising:

Claims (9)

An optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
The optical transmitter
A first light source that emits continuous light having a variable wavelength;
First wavelength changing means for changing a wavelength of light emitted from the first light source at a first changed frequency specific to an assigned transmission channel;
With
An optical receiver that receives an optical signal from the optical transmitter,
Frequency detecting means for detecting a second changed frequency from a change in wavelength based on the wavelength of the light emitted from the first light source based on the received optical signal;
Channel identification means for confirming that an optical signal has been received from a desired receiving channel when the detected second changed frequency matches the first changed frequency specific to the assigned transmission channel;
An optical communication system comprising: The optical receiver is
A second light source that emits continuous light whose wavelength can be changed, wherein the second light source emits light having the same wavelength as the light emitted by the first light source in order to cause interference with an optical reception signal;
Second wavelength changing means for changing a wavelength of light emitted from the second light source at the second changed frequency detected by the frequency detecting means;
Further comprising
2. The optical communication system according to claim 1, wherein the frequency detection unit detects the second change frequency based on an optical reception signal interfered with continuous light emitted from the second light source. An optical communication method of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
A wavelength changing step in which the optical transmitter changes the wavelength of the continuous light emitted by the first light source at a first changed frequency specific to the assigned transmission channel;
A frequency detection step in which the optical receiver detects a second change frequency from a change in wavelength based on the wavelength of the light emitted from the first light source, based on the received optical signal;
A channel identification step for confirming that the optical receiver has received an optical signal from a desired reception channel when the detected second modified frequency matches the first modified frequency specific to the assigned transmission channel; When,
An optical communication method comprising: The optical transmitter of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
A first light source that emits continuous light having a variable wavelength;
Wavelength changing means for changing the wavelength of the light emitted by the first light source at a first changing frequency specific to the assigned transmission channel;
An optical transmitter comprising: A method of controlling the optical transmitter of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
A method for controlling an optical transmitter, comprising: a wavelength changing step of changing a wavelength of continuous light emitted from a first light source at a first changing frequency specific to an assigned transmission channel. The optical receiver of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
Frequency detecting means for detecting a second changed frequency from a change in wavelength based on the wavelength of light emitted from the first light source of the optical transmitter based on the received optical signal;
The detected second change frequency is a first change frequency specific to a transmission channel assigned to the optical transmitter, and the optical transmitter changes the wavelength of light emitted from the first light source. Channel identification means for confirming that an optical signal has been received from a desired reception channel when the first change frequency used is matched;
An optical receiver comprising: A method for controlling the optical receiver of an optical communication system in which an optical transmitter and an optical receiver are connected by an optical transmission line,
A frequency detecting step of detecting a second changed frequency from a change in wavelength based on the wavelength of light emitted from the first light source of the optical transmitter based on the received optical signal;
The detected second change frequency is a first change frequency specific to a transmission channel assigned to the optical transmitter, and the optical transmitter changes the wavelength of light emitted from the first light source. A channel identification step for confirming that an optical signal is received from a desired reception channel when the first change frequency used is matched;
An optical receiver control method comprising: An optical transceiver for transmitting and receiving optical signals,
A light source that emits continuous light whose wavelength can be changed;
Wavelength changing means for changing the wavelength of light emitted by the light source at a first changing frequency specific to the assigned transmission channel;
Frequency detecting means for detecting a second changed frequency from a change in wavelength based on the wavelength of the light emitted from the light source of the transmission source based on the received optical signal;
The detected second change frequency is a third change frequency specific to a transmission channel assigned to the transmission source, and is used to change the wavelength of light emitted from the light source of the transmission source at the transmission source. Channel identification means for confirming that an optical signal has been received from a desired reception channel when the third changed frequency matches,
An optical transceiver characterized by comprising: An optical transceiver control method for transmitting and receiving an optical signal,
A wavelength changing step for changing a wavelength of continuous light emitted by the light source at a first changing frequency specific to the assigned transmission channel;
A frequency detection step of detecting a second changed frequency from a change in wavelength based on the wavelength of the light emitted from the light source of the transmission source based on the received optical signal;
The detected second change frequency is a third change frequency specific to a transmission channel assigned to the transmission source, and is used to change the wavelength of light emitted from the light source of the transmission source at the transmission source. A channel identifying step for confirming that an optical signal has been received from a desired receiving channel when the third changed frequency matches,
An optical transceiver control method comprising:

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