Optical transceiver, optical transmission system, and carrier interval control method for optical transceiver

Abstract

To optimally adjust a plurality of optical frequency intervals for optical transmission.SOLUTION: The transceiver 100 includes a plurality of optical modulators 132 that generate optical signals obtained by optically modulating a plurality of light beams having a carrier interval Δ fr of the multi-wavelength light source 101 based on data, and an optical multiplexer 133 that multiplexes the optical signals having a channel frequency interval Δ ftmx and transmits and outputs the multiplexed optical signal. It also includes an optical demultiplexer 141 that demultiplexes a received optical signal with the channel frequency spacing Δ frdmx, and a plurality of optical receivers 142 that perform coherent detection of a plurality of optical signals and demodulate data. The controller 120 controls the carrier interval output by the multi-wavelength light source 101 so that the optical power of the optical signal output by the optical demultiplexer 141 is maximized, and adjusts the deviation of the channel frequency interval output by the optical multiplexer 133 with respect to the carrier interval.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an optical transceiver, an optical transmission system, and a carrier spacing control method for an optical transceiver. [Background technology]

[0002] To cope with the ever-increasing traffic in optical networks, the introduction of multiband transmission technology is being promoted to increase the number of wavelength multiplexed channels and expand transmission capacity. Multicarrier optical transceivers use a multi-wavelength light source such as a comb light source in the transmitter, transmit orthogonally polarized coherent light in which the signal is modulated by the amplitude and phase of multiple carriers, and demodulate the multiple signals by coherent detection in the receiver.

[0003] Prior art techniques include, for example, a technique for detecting frequency mismatches between optical signals of multiple frequencies transmitted and received by an optical frequency comb source by observing beat frequency components generated on the receiving side and adjusting the phase of local light to match the input signal (see, for example, Patent Documents 1 and 2 below). Another technique involves transmitting a modulated signal created by phase modulation and reference light to multiple sidebands generated by an optical frequency comb generator on the transmitting side, and demodulating the modulated signal on the receiving side based on the multiple sidebands generated by the optical frequency comb generator based on the reference light (see, for example, Patent Document 3 below). Another technique involves generating a frequency comb signal containing a pilot tone and an optical tone using a frequency comb source on the transmitting side, transmitting the optical tone as coherent light, and demodulating the coherent light on the receiving side using a frequency comb source driven by the pilot tone (see, for example, Patent Document 4 below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2009-524351 [Patent Document 2] U.S. Patent Application Publication No. 2007 / 0166048 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-298553 [Patent Document 4] U.S. Patent No. 1,1750,357 Summary of the Invention [Problem to be solved by the invention]

[0005] In the comparative example, the center frequency of the comb light source and the filter phase of the multiplexer (Mx, optical multiplexer) and demultiplexer (Dmx, optical demultiplexer) are adjusted by controlling the temperature of the arrayed waveguide gratings (AWG). However, a discrepancy occurs between the carrier spacing of the comb light source and the channel frequency spacing of Mx / Dmx. As will be described in detail later, this discrepancy in the channel frequency spacing is caused by variations in the refractive index distribution on the chip surface that makes up the AWG. The frequency discrepancy between Mx / Dmx between a pair of transceivers causes signal degradation such as Q factor degradation, limiting the parallelism (number of carriers) of optical transmission.

[0006] In one aspect, the present invention aims to be able to optimally adjust the spacing between a plurality of optical frequencies to be transmitted. [Means for solving the problem]

[0007] According to one aspect of the present invention, an optical transceiver includes a multi-wavelength light source that outputs light of multiple optical frequencies having a predetermined carrier spacing, a transmitter, a receiver, and a controller, wherein the transmitter includes a plurality of optical modulators that generate optical signals by optically modulating each of the multiple light beams output by the multi-wavelength light source based on data, and an optical combiner that combines the optical signals output by the multiple optical modulators with a predetermined channel frequency spacing and outputs the combined optical signals to a transmission optical transmission path, wherein the receiver includes an optical demultiplexer that demultiplexes the optical signal on the reception optical transmission path into a plurality of optical signals having a predetermined channel frequency spacing, and a plurality of optical receivers that coherently detect each of the multiple optical signals output by the optical demultiplexer using light from the multi-wavelength light source and demodulate the data, and the controller controls the carrier spacing output by the multi-wavelength light source based on the optical power of the optical signal output by the optical demultiplexer of the receiver, and adjusts the channel frequency spacing output by the optical combiner of the transmitter relative to the carrier spacing. [Effects of the Invention]

[0008] According to one aspect of the present invention, it is possible to optimally adjust the intervals between a plurality of optical frequencies to be optically transmitted. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 illustrates an example of the configuration of an optical transceiver according to an embodiment. [Figure 2] FIG. 2 is an explanatory diagram of the system configuration and problems of the comparative example. [Figure 3] FIG. 3 is a diagram showing the refractive index distribution within the wafer surface in silicon photonics. [Figure 4] FIG. 4 is an explanatory diagram of signal degradation due to a frequency interval deviation at Mx / Dmx between a pair of transmitting and receiving transceivers. [Figure 5A] FIG. 5A is an explanatory diagram of Q-factor degradation due to frequency spacing deviation at Mx / Dmx between a pair of transmitting and receiving transceivers (part 1). [Figure 5B]FIG. 5B is an explanatory diagram of Q-factor degradation due to frequency spacing deviation at Mx / Dmx between a pair of transmitting and receiving transceivers (part 2). [Figure 6] FIG. 6 is an explanatory diagram of carrier interval control according to the embodiment. [Figure 7] FIG. 7 is a diagram illustrating power fluctuations due to deviations in channel frequency intervals. [Figure 8] FIG. 8 illustrates an example of the hardware configuration of a controller of the optical transceiver. [Figure 9] FIG. 9 is a flowchart showing an example of control by the controller. [Figure 10] FIG. 10 is an explanatory diagram illustrating an example of control of the entire optical transmission system according to the embodiment. [Figure 11] FIG. 11 is a sequence diagram of an example of control of the entire optical transmission system according to the embodiment. [Figure 12A] FIG. 12A is a diagram illustrating an example of convergence by performing control according to the embodiment. [Figure 12B] FIG. 12B is a diagram showing the spectral distribution of the outermost channel before and after the control. [Figure 13A] FIG. 13A is an explanatory diagram of the effect of the embodiment (part 1). [Figure 13B] FIG. 13B is an explanatory diagram of the effect of the embodiment (part 2). [Figure 14] FIG. 14 is a diagram illustrating an example of the configuration of an optical transceiver according to another embodiment. [Figure 15] FIG. 15 is an explanatory diagram showing an example of control of the entire optical transmission system according to another embodiment. [Figure 16A] FIG. 16A is a sequence diagram of an example of control of the entire optical transmission system according to another embodiment. [Figure 16B] FIG. 16B is a diagram illustrating an example of VCO frequency control according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, with reference to the drawings, detailed descriptions will be given of embodiments of the disclosed optical transceiver, optical transmission system, and carrier spacing control method for the optical transceiver. The optical transceiver described in the embodiments is, for example, a multi-carrier coherent transceiver that transmits multi-carrier coherent light. The optical transceivers are arranged on the transmitting side and the receiving side of a transmission section of a WDM (Wavelength Division Multiplexing) optical transmission system.

[0011] An optical transceiver transmits a frequency-multiplexed optical signal onto an optical transmission line, where the transmitter transmits multiple signals at multiple optical frequency intervals on each carrier using optical modulation.The receiver extracts the multiple signals from the optical transmission line by frequency-separating, demodulating, and decoding the optical signal.

[0012] As will be explained below, an optical transmission system has a pair of optical transceivers arranged facing each other on the transmitting and receiving sides of a transmission section. For example, a pair of optical transceivers has a transmitter on the transmitting side of an upstream optical transmission path and a receiver on the receiving side, and a transmitter on the transmitting side of a downstream optical transmission path and a receiver on the receiving side. That is, one optical transceiver has a transmitter on the transmitting side of the upstream optical transmission path and a receiver on the downstream optical transmission path.

[0013] 1 is a diagram illustrating an example of the configuration of an optical transceiver according to an embodiment. The optical transceiver (hereinafter also referred to as transceiver, Xcvr#1) 100 includes a multi-wavelength light source 101, a controller (Ctrl) 120, a transmitter 130, and a receiver 140.

[0014] 1 includes a laser light source 111, a phase modulator (including a ring resonator) 112, and a VCO (Voltage Controlled Oscillator) 113. The laser light source 111 emits a laser beam having a frequency f s1 The phase modulator 112 outputs light, for example, continuous wave light (CW), to the phase modulator 112. The phase modulator 112 adjusts the carrier interval Δf r1and outputs a plurality of lights (four waves in the example of FIG. 1) having the above-mentioned characteristics to the transmitter 130 and the receiver 140.

[0015] The transmitter 130 includes an optical demultiplexer (Dmx) 131, an optical modulator (IQ Mod) 132, and an optical multiplexer (Mx) 133. The optical demultiplexer (Dmx) 131 modulates the carrier interval Δf output from the phase modulator 112. r1 Light with a carrier spacing of Δf r1 The channel frequency spacing Δf tmx1 It is split into multiple waves (four waves in the example of Figure 1).

[0016] The number of optical modulators 132 (four units) corresponds to the number of demultiplexing waves (four waves), and each of the optical modulators 132a to 132d is, for example, a Mach-Zehnder modulator, and adds different data to the optical signal by IQ optical modulation. The optical multiplexer (Mx) 133 multiplexes the optical signals output from the plurality (four units) of optical modulators 132 (132a to 132d), and outputs the multiplexed optical signals to one of the optical transmission paths 150a (downstream for transmission). The optical signals output from the optical multiplexer (Mx) 133 are separated by a channel frequency interval Δf tmx1 The optical transmission line 150 is made up of an optical fiber, an optical waveguide, or the like.

[0017] The receiver 140 includes optical demultiplexers (Dmx) 141 and 143, and an optical receiver 142. The optical demultiplexer (Dmx) 141 divides the optical signals transmitted through the other (upstream receiving) optical transmission line 150b of the optical transmission lines 150 into optical signals having a channel frequency interval Δf rdmx1 The optical signal is split into a plurality of waves (four waves in the example of FIG. 1) and output to the optical receiver 142.

[0018] The optical demultiplexer (Dmx) 141 has an optical monitor that detects the optical power of the optical signal at a plurality of output ports that demultiplex and output the optical signals. In the example of FIG. 1, the optical demultiplexer (Dmx) 141 is provided with an optical monitor 141d at the outermost output port of the received optical signal to detect the optical power (P mN The outermost output port is an output port that outputs the subcarrier at the edge of the signal band, that is, the subcarrier at the maximum or minimum center frequency of the optical spectrum of the subcarrier of the optical signal.

[0019] The optical demultiplexer (Dmx) 143 demultiplexes the carrier interval Δf r1 Light with this carrier spacing Δf r1 The channel frequency spacing Δf rdmx1 The optical signal is split into a plurality of waves (four waves in the example of FIG. 1) and output to the optical receiver 142 as LO light.

[0020] The number of optical receivers 142 (four) corresponds to the number of demultiplexed waves (four waves), and the optical receivers 142a to 142d demodulate the optical signals of each of the four demultiplexed channels by coherent detection using the LO light of the multi-wavelength light source 101.

[0021] In the embodiment, the optical multiplexer (Mx) 133 of the transmitter 130 and the optical demultiplexer (Dmx) 141 of the receiver 140 may be formed in the same optical integrated circuit (the same optical chip).

[0022] The multi-wavelength light source 101 has a carrier spacing Δf r1 It is sufficient to output a plurality of light beams having the above frequencies, and it may be configured as an array light source that outputs light beams of the plurality of frequencies. When an array light source is used for the multi-wavelength light source 101, the light beams of the plurality of frequencies are output directly to a plurality of optical modulators 132 and optical receivers 142. In this case, the optical demultiplexers (Dmx) 131 and 143 shown in FIG. 1 are not necessary.

[0023] The controller (Ctrl) 120 controls the carrier interval Δf output by the phase modulator 112. r1 The controller (Ctrl) 120 performs the following controls 1 to 4. 1. The optical power (P mN ) to detect. 2. The current monitor value detected by the optical monitor 141d is compared with the previous monitor value, and the carrier interval Δf is adjusted so that the optical power detected by the optical monitor 141d becomes the maximum value. r1 Determine the direction of increase or decrease. 3. Determined carrier spacing Δf r1The carrier interval Δf output by the phase modulator 112 of the transmitter 130 varies depending on the direction of increase or decrease of r1 is increased or decreased by a predetermined amount (δ). 4. As a result, the transmitter 130 receives the signal from the optical multiplexer (Mx) 133, which has a channel frequency interval Δf tmx1 The optical signal having the following formula is output to the optical transmission line 150a.

[0024] The controller (Ctrl) 120 repeats the above-mentioned steps 1 to 4 to adjust the carrier interval Δf r1 (The channel frequency interval Δf tmx1 ) is optimized. r1 (The channel frequency interval Δf tmx1 The necessity of optimizing the above will be explained below, along with comparative examples and issues.

[0025] (Comparative Examples and Their Problems) Fig. 2 is an explanatory diagram of a system configuration and problems of a comparative example. Fig. 2 shows an example of a system configuration in which a pair of transceivers 200 are arranged across an optical transmission line 250. In each configuration of transceiver 200, components that are the same as those in Fig. 1 are indicated by reference numerals in the 200 range.

[0026] The configuration of one transceiver 1 (Xcvr#1) 200 will be explained. A multi-wavelength light source 201 has a carrier spacing Δf r1 The transmitter 230 and the receiver 240 are output with a plurality of (four) waves of light having the above configuration.

[0027] The transmitter 230 uses an optical multiplexer (Mx) 233 to separate the channel frequencies by Δf tmx1 The receiver 240 outputs an optical signal having a channel frequency interval Δf to the optical transmission line 250a. rdmx1 The wavelengths are separated by the

[0028] The other transceiver 2 (Xcvr#2) 200 has the same configuration as transceiver 1 (Xcvr#1), and the multi-wavelength light source 201 has a carrier spacing Δf r2The transmitter 230 and the receiver 240 are output with a plurality of (four) waves of light having the above configuration.

[0029] The receiver 240 divides the optical signal input from the optical transmission line 250a by the optical demultiplexer (Dmx) 241 into a channel frequency interval Δf rdmx2 The transmitter 230 separates the wavelengths by using an optical multiplexer (Mx) 233 to separate the channels into a frequency interval Δf tmx2 and outputs the optical signal having the following to the optical transmission line 250b.

[0030] The optical multiplexer (Mx) 233 and the optical demultiplexer (Dmx) 241 are formed of, for example, an arrayed waveguide grating (AWG) using silicon photonics (SiPh) technology. The adjustment of the center frequency of the multi-wavelength light source 201 such as a comb light source and the filter phase of the optical multiplexer (Mx) 233 and the optical demultiplexer (Dmx) 241 are controlled by adjusting the temperature of the AWG.

[0031] However, in the comparative example, the occurrence of a frequency deviation between the carrier interval of the multi-wavelength light source 201 and the channel frequency interval of the optical multiplexer (Mx) 233 and the optical demultiplexer (Dmx) 241 is not taken into consideration.

[0032] The carrier interval is Δf rn , the design value (fixed value) of the channel frequency interval of Mx / Dmx is Δf tmxn ,Δf rdmxn Then, Δf within the same transceiver 200 (within the same optical IC) tmxn ≒Δf rdmxn (~0.1% deviation).

[0033] The optical signal seen in the optical transmission of the downstream optical transmission line 250b has a carrier interval Δf r2 , Mx channel frequency interval Δf tmx2 The error in wavelength spacing between the receiver 240 and the receiver 240 on the receiving side (Xcvr#1) is 1% (1 GHz for 100 GHz, details will be described later). tmx1 , the carrier spacing of the LO light is Δf r1Carrier spacing Δf r1 can be compensated for by controlling the DSP or the like on the receiving side (Xcvr#1). In the example of FIG. 2, the channel frequency interval Δf tmx2 is narrow, whereas the channel frequency interval of Dmx241 of receiver 240 on the receiving side (Xcvr#1) is Δf tmx1 is spreading, resulting in a deviation of 1 GHz.

[0034] Figure 3 is a diagram showing the refractive index distribution within a wafer surface in silicon photonics. Figure 3 is disclosed in Figure 2(b) of Non-Patent Document 1 below, and the refractive index varies at each position within the wafer surface (X 15 mm, Y 9 mm).

[0035] Non-Patent Document 1: “Impact of Fabrication Non-Uniformity on Chip-Scale Silicon Photonic Integrated Circuits”, L. Chrostowski, et al., Department of Electrical and Computer Engineering, University of British Columbia, V6R 1T3, Canada, Th2A.37.pdf, OFC 2014 OSA 2014.

[0036] Here, the signal light wavelength Λ, the group refractive index of the waveguide n g , when the difference in the length of both arms in the asymmetric MZ (Mach-Zehnder interferometer) is ΔL, Δf dmx ∝λ 2 / (2×n g ×ΔL).

[0037] On the wafer surface area shown in FIG. 3, for example, Mx and Dmx are cut out at different positions with a square of about 1 mm. g When =4.225~4.265, Δn g is about 1%. Δf dmx = 100GHz design, Δf dmx3, a deviation of about 1 GHz occurs within the wafer surface, which results in a deviation of about 1 GHz between a pair of transmitting and receiving transceivers (Xcvr#2 to Xcvr#1). Looking at this in terms of Mx / Dmx corresponding to optical subcarriers with N wavelengths, the optical frequency position from one end of the wavelength band of the optical signal to the other end will deviate from the design value by N × 1 GHz.

[0038] Figure 4 is an explanatory diagram of signal degradation due to frequency spacing misalignment between a pair of transmitting and receiving transceivers (Mx / Dmx). The horizontal axis represents frequency, and the vertical axis represents optical power. The optical spectrum of the transmitted optical signal has a nearly trapezoidal filter characteristic.

[0039] 4 shows the optical transmission state of the optical signal on the downstream optical transmission line 250b, as in FIG. 2. The carrier interval of the transmitter 230 on the transmitting side (Xcvr#2) is set to Δf r2 , the channel frequency interval of Mx 233 of the transmitter 230 is Δf tmx2 , the channel frequency interval of the Dmx 241 of the receiver 240 on the opposite receiving side (Xcvr#1) is Δf rdmx1 4, the filter characteristics of Mx 233 of the transmitter 230 are shown by a solid line, and the filter characteristics of Dmx 241 of the receiver 240 are shown by a dotted line.

[0040] As shown in Fig. 4(a), suppose that a deviation (error) occurs in the frequency interval between the filter characteristics (solid line) of Mx 233 of transmitter 230 and the filter characteristics (dotted line) of Dmx 241 of receiver 240. In this case, as shown in Fig. 4(b), the signal spectrum received by the opposing transceiver (Xcvr#1) is cut, narrowing the signal band, degrading the signal components and causing a deterioration in the Q value.

[0041] As shown in FIG. 4(a), the center wavelength of the signal band is f r Although the phase of Mx / Dmx has already been adjusted, the frequency deviation error accumulates and becomes larger at either end of the signal band.

[0042] Here, as shown in Figure 4(c), signal degradation can be suppressed by providing a guard band to correspond to the difference in frequency spacing between Mx233 on the transmitting side and Dmx241 on the receiving side, but the frequency spacing of the subcarriers will become larger, resulting in reduced spectral efficiency.

[0043] 5A and 5B are diagrams illustrating degradation of the Q factor due to a frequency spacing deviation between a pair of transmitting and receiving transceivers Mx / Dmx. As shown in FIG. 5A, the filter characteristics of Mx 233 (solid line) and the filter characteristics of Dmx 241 are different when there is a frequency spacing deviation of ±X% (Δf tmx ≠Δf rdmx In this case, both sides of the subcarrier signal tail are narrowed by the amount indicated by the arrows in the figure due to the interval (guard band) between the tails of Mx233 / Dmx241. The narrowing amount is (N / 2-1) × X × CH spacing (N: number of subcarriers).

[0044] As the number of subcarriers increases, the error between the carrier spacing and the channel frequency spacing accumulates. The horizontal axis of Fig. 5B(a) represents the frequency spacing offset (%), and the vertical axis represents the Q-factor penalty (dB).

[0045] Figure 5B(b) shows the Q-factor penalty (dB) and total data bandwidth (Tbps) for each number of subcarriers, N. Assume that the optical signal to be transmitted is 66 GBd, DP16QAM, the Mx / Dmx channel (frequency) spacing is 75 GHz, and the ENOB (effective number of bits performed by the DAC / ADC) is 4. DP16QAM stands for Dual Polarization 16 Quadrature Amplitude Modulation.

[0046] When the number of subcarriers is N=8 (3.2 Tbps class), the Q-factor penalty is about 1.2 dB. If the number of subcarriers N (degree of parallelism) is further increased, the Q-factor penalty will be several dB.

[0047] On the other hand, when there is a limit on the Q factor, the degree of parallelism (number of carriers) is limited due to the Q factor penalty. In Figure 5B(a), up to N = 8, error correction is possible within the Q factor limit, but at N = 16, the Q factor limit is exceeded and error correction becomes impossible. Thus, in the comparative example, if the degree of parallelism is increased to increase the number of subcarriers, it becomes impossible to suppress the occurrence of the Q factor penalty.

[0048] (Control example of embodiment) FIG. 6 is an explanatory diagram of carrier interval control according to the embodiment. FIG. 6(a) shows a comparison of the frequency interval deviation similar to that of FIG. 4(a) of the comparative example. In the embodiment, in order to solve the above problem, as shown in FIG. 6(b), the carrier interval Δf r The channel frequency interval Δf tmx and the channel frequency interval Δf of the Dmx 141 of the receiver 140. rdmx and the intermediate value ({Δf tmx2 +Δf rdmx1} / 2) This suppresses the frequency interval deviation and reduces the amount of narrowing described above.

[0049] Furthermore, in the embodiment, within the same transceiver 200 (for example, within the same optical IC of Xcvr#1), the optical multiplexer (Mx) 233 and optical demultiplexer (Dmx) 241 located on the optical transmission line 150 side are formed using the same optical integrated circuit (the same optical chip). This allows the filter characteristics (errors) of the optical multiplexer (Mx) 233 and the optical demultiplexer (Dmx) 241 within the same transceiver 200 to be approximately the same, minimizing the frequency spacing deviation in the initial state.

[0050] 7 is an explanatory diagram of power fluctuations due to deviations in channel frequency spacing. In the embodiment, an example of carrier spacing control using power fluctuations due to deviations in channel frequency spacing will be described.

[0051] Figure 7(a) shows the filter characteristics of Mx / Dmx, where the horizontal axis is frequency and the vertical axis is optical power. Mx / Dmx is a rectangular filter and the signal rectangular spectrum is estimated. The carrier spacing is 1.17 times the signal bandwidth (carrier spacing 75 GHz, rate 64 GBd).

[0052] Figure 7(b) shows the characteristics for different frequency spacing offsets between Mx and Dmx, with the horizontal axis representing the frequency spacing offset and the vertical axis representing optical power. For example, the (-3, 4) characteristic indicates that the frequency spacing offset for Mx is 3% smaller and that for Dmx is 4% larger. The figure shows the calculation results for optical power versus frequency offset (%) of the signal spectrum.

[0053] According to Fig. 7(b), the carrier interval Δf r is the channel frequency interval Δf tmx and the channel frequency interval Δf of the Dmx of the opposite receiver rdmx The optical power is maximized when the offset is at the midpoint of the carrier interval Δf. If a guard band is present, the range of offsets where the optical power is maximized will be wider. Therefore, in this embodiment, the receiver monitors the optical power of each channel, and the carrier interval Δf r By controlling the carrier spacing Δf r This makes it possible to achieve optimal control of the

[0054] For example, in the example of FIG. 1, the optical monitor 141d of the Dmx 141 of the receiver 140 detects a channel frequency interval Δf rdmx1 The controller 120 monitors the maximum value of the optical power of the outermost frequency of the carrier interval Δf r1 As shown in FIG. 4(a), the frequency spacing deviation of the subcarrier (channel) at the outermost frequency of the signal band is the largest, so it is effective to detect the optical power of this outermost frequency and use it for control. In the embodiment, as described above, the carrier spacing Δf r1 By controlling the carrier spacing Δf r1 and the channel frequency interval Δf of Mx133 tmx1 and align them.

[0055] (Controller configuration example) 8 is a diagram illustrating an example of the hardware configuration of the controller of the optical transceiver, which illustrates an example of the configuration of the controller 120, which corresponds to the control unit of the optical transceiver 100 illustrated in FIG.

[0056] 8, the controller 120 includes a processor 801 such as a CPU (Central Processing Unit), a memory 802, a network IF 803, a recording medium IF 804, and a recording medium 805. The components are connected to each other via a bus 800.

[0057] Here, the processor 801 is a control unit that controls the entire optical transceiver 100. The processor 801 may have multiple cores. The memory 802 includes, for example, a read-only memory (ROM), a random access memory (RAM), and a flash ROM. Specifically, for example, the flash ROM stores a control program, the ROM stores an application program, and the RAM is used as a work area for the processor 801. The programs stored in the memory 802 are loaded into the processor 801, causing the processor 801 to execute the coded processes.

[0058] The network IF 803 serves as an interface between the network NW and the control unit (controller 120), and controls input and output of information between the optical transceiver 100 and the outside.

[0059] The recording medium IF 804 controls reading / writing of data from / to the recording medium 805 under the control of the processor 801. The recording medium 805 stores the data written under the control of the recording medium IF 804.

[0060] In addition to the above-mentioned components, the control unit (controller 120) may be connectable to, for example, an input device, a display, etc. via an IF.

[0061] The processor 801 shown in Fig. 8 executes a program to realize the functions of the controller 120 of the optical transceiver 100 shown in Fig. 1. The controller 120 may also be configured with an FPGA (Field-Programmable Gate Array), an ASIC (Application Specific Integrated Circuit), or a DSP (Digital Signal Processor).

[0062] (Controller control example) 9 is a flowchart showing an example of control by the controller 120. The controller 120 performs the following controls 1 to 3 for each of its own transceivers 100 asynchronously with the opposing transceivers.

[0063] 1. The optical power (P mN The outermost output port is the output port with the maximum or minimum center frequency of the subcarrier (channel) optical spectrum. 2. The carrier interval is controlled so that the monitor value (optical power) of the optical monitor 141d is maximized. For example, the current monitor value P mN and the previous monitor value P mN Compare (t-1), P mN (t-1)≦P mN In this case, the direction of increase / decrease of the carrier spacing (the direction of increase / decrease relative to the frequency) is not changed. P mN (t-1)>P mN If so, the direction of increase or decrease of the carrier interval is reversed. 3. Carrier spacing Δf r Increase or decrease the value and send it. Δf r =Δf r (t-1)+δ (δ: carrier interval adjustment amount)

[0064] An example of control will be described below with reference to Fig. 9. In Fig. 9, the control flow indicated by the solid lines shows control relating to carrier spacing, and the dotted lines show control relating to the device operation of the transceiver 100 itself.

[0065] First, the controller 120 measures the optical power P mN is measured (step S901).

[0066] The controller 120 then determines whether the measured optical power is P mN It is determined whether the optical power is P > 0 (step S902). mN If it is >0 (step S902: Yes), the controller 120 proceeds to the control of step S903, and the optical power is set to P mN If it is not >0 (step S902: No), the control proceeds to step S904.

[0067] In step S903, the controller 120 calculates the measured monitor value P mN is stored in the storage unit (step S903), and the control proceeds to step S905. The storage unit may be, for example, the memory 802 shown in FIG. 8. The stored monitor value P mN The next time control is performed, the previous monitor value P mN It is used as (t-1).

[0068] In step S904, controller 120 determines that the error is in its own transceiver 100, and performs a predetermined transceiver error process (step S904), after which the above process ends.

[0069] In step S905, the controller 120 calculates the carrier spacing Δf r For example, adjust Δf r =Δf r +δ adjusts the carrier interval Δf by the amount of adjustment δ. r Increase the

[0070] Next, the controller 120 again monitors the optical power P mN (step S906). Then, the controller 120 measures the previous monitor value P mN(t-1) is read from the memory, and the current monitor value P mN The absolute value of the difference between min Below(|P mN (t-1)-P mN |≦ΔP min ) (step S907).

[0071] If the condition in step S907 is not met, the controller 120 mN (t-1)-P mN |>ΔP min , step S907: No), the process proceeds to step S909. In step S909, the controller 120 calculates the previous monitored value P mN (t-1) is the current monitor value P mN Below (P mN (t-1)≦P mN ) (step S909).

[0072] Judgment result, previous monitor value P mN (t-1) is the current monitor value P mN Below (P mN (t-1)≦P mN ) (step S909: Yes), the controller 120 returns to the control of step S903. mN (t-1) is the current monitor value P mN Below (P mN (t-1)≦P mN If not (step S909: No), the controller 120 reverses (-δ) the direction of carrier interval adjustment (step S910), and returns to the control of step S903.

[0073] If the condition in step S907 is satisfied, the controller 120 mN (t-1)-P mN |≦ΔP min, step S907: Yes), and turns ON a convergence flag indicating that the above control of the carrier interval has converged (step S908), and ends the above control. However, the present invention is not limited to this, and the controller 120 may proceed to the control of step S909 after a predetermined period of time, such as a fixed time, has elapsed in order to continue monitoring the carrier interval even after the control of step S908 has been performed.

[0074] (Example of control over the entire optical transmission system according to the embodiment) 10 is an explanatory diagram showing an example of control of the entire optical transmission system according to the embodiment. In FIG. 10, the same components as those in FIG. 1 are assigned the same reference numerals. An example of control performed by the controllers 120, 120 of a pair of transceivers (Xcvr#1, Xcvr#2) in the transmission system in cooperation with each other will be described. Here, one transceiver (Xcvr#1) transmits a CW light of frequency f s1 , carrier spacing Δf r1 , the channel frequency interval Δf tmx1 , receiving channel frequency interval Δf rdmx1 The other transceiver (Xcvr#2) transmits CW light at frequency f s2 , carrier spacing Δf r2 , the channel frequency interval Δf tmx2 , receiving channel frequency interval Δf rdmx2 is.

[0075] In the example of cooperative control in FIG. 10, first, the controller (Ctrl) 120 of one transceiver (Xcvr#2) performs the following controls 1. to 3. 1. The optical power (P mN ) to detect. 2. The carrier interval Δf output by the phase modulator 112 of the transmitter 130 increases in the direction in which the current monitor value detected by the optical monitor 141d increases. r2 Control. 3. With the updated carrier spacing, the transmitter 130 determines whether the Mx 133 is in the channel frequency interval Δf tmx2 The optical signal having the above formula is transmitted and output to the optical transmission line 150b.

[0076] Next, the controller (Ctrl) 120 of the other transceiver (Xcvr#1) performs the following controls 4. to 6. 4. The optical power (P mN ) to detect. 5. The carrier interval Δf output by the phase modulator 112 of the transmitter 130 increases in the direction in which the current monitor value detected by the optical monitor 141d increases. r1 Control. 6. With the updated carrier interval, the transmitter 130 adjusts the channel frequency interval Δf tmx1 The optical signal having the above formula is transmitted and output to the optical transmission line 150a.

[0077] Fig. 11 is a sequence diagram of an example of control of the entire optical transmission system according to the embodiment. Fig. 11(a) shows the above-mentioned Controls 1 to 6 of each controller (Ctrl) 120 of a pair of transceivers (Xcvr#1, Xcvr#2) and an example of frequency control of each VCO 113, corresponding to the control example of Fig. 10.

[0078] 11(b) to (f) show the channel frequency interval Δf of the optical signal Tx to be transmitted and the optical signal Rx to be received, which are controlled by changing the frequency setting of each VCO 113. tmx1 , Δf tmx2 , the receiving channel frequency interval Δf rdmx1 , Δf rdmx2 The change in frequency (horizontal axis) is shown as a vertical position.

[0079] In the initial state of control shown in FIG. 11(a), the filters of Mx 133 and Dmx 141 and the center frequency of the laser light source 111 are the same (FIG. 11(b)). In the initial state (0), the transceiver Xcvr#1 uses a carrier interval Δf r1 (0), receiving channel frequency interval Δf rdmx1 The transmission optical signal Tx1 and the reception optical signal Rx1 are spaced apart by a channel frequency interval Δf tmx1 ,Δf rdmx1 Also, Xcvr#2 has a carrier interval Δf r2 (0), receiving channel frequency interval Δfrdmx2 The optical signals Tx2 and Rx2 transmitted and received are spaced at a channel frequency interval Δf rdmx2 , Δf tmx2 It has.

[0080] Then, during the first (1) adjustment control, the transceiver Xcvr#1 transmits an optical signal (data transfer). As a result, the transceiver Xcvr#2: 1. The optical monitor 141d of the Dmx 141 of the receiver 140 detects the optical power (P mN 2. The carrier interval Δf output by the phase modulator 112 of the transmitter 130 is detected in the direction in which the current monitor value detected by the optical monitor 141d increases. r2 By implementing the control corresponding to the frequency spacing deviation, the channel frequency spacing Δf rdmx2 (1) will be changed.

[0081] After this, the transceiver Xcvr#2 3. updates the carrier interval so that the Mx 133 of the transmitter 130 has the channel frequency interval Δf tmx2 The optical signal having the above-mentioned value is transmitted (data transfer) to the optical transmission line 150b.

[0082] After this, the transceiver Xcvr#1 measures the optical power (P mN ) is detected. 5. The carrier interval Δf output by the phase modulator 112 of the transmitter 130 is then detected in the direction in which the current monitor value detected by the optical monitor 141d increases. r1 By implementing control to deal with the frequency spacing deviation, the channel frequency spacing Δf rdmx1 (1) will be changed.

[0083] After this, during the second (2) adjustment control, the transceiver Xcvr#1 adjusts the channel frequency interval Δf tmx1 An optical signal having (1) is transmitted and output to the optical transmission line 150a.

[0084] Thereafter, the controllers (Ctrl) 120 of the pair of transceivers (Xcvr#1, Xcvr#2) repeatedly execute the above-described controls 1 to 6. By the above-described control for reducing the difference between the carrier interval and the channel frequency interval, the channel frequency interval Δf of the optical signals Tx1, Rx1, Tx2, and Rx2 transmitted and received by each other in the entire optical transmission system is reduced as shown in FIGS. rdmx2 ,Δf rdmx1 can be gradually brought closer.

[0085] 12A is a diagram showing an example of convergence by implementing control according to the embodiment. The horizontal axis of FIG. 12A is time, the vertical axis (left side) is frequency, and the number of subcarriers (SC) is 16. The vertical axis (right side) also shows monitor values ​​1 and 2 detected by the outermost channel (outermost output port, optical monitor 141d).

[0086] The pair of transceivers 100 are such that Xcvr#1 has a channel frequency interval Δf tmx1 ,Δf rdmx1 , Xcvr#2 is the channel frequency interval Δf tmx2 ,Δf rdmx2 At the start of control (time 0), the optical powers of the monitor values ​​1 and 2 of the pair of transceivers 100 (Xcvr#1, Xcvr#2) are weak, and the carrier interval (Δf r1 ,Δf r2 ) is outside the range of the predetermined threshold Th. However, by implementing the above control, the carrier interval (Δf r1 ,Δf r2 ) quickly converges to within the range of the threshold value Th.

[0087] Figure 12B shows the spectral distribution of the outermost channel before and after control. The horizontal axis represents frequency, and the vertical axis represents optical power. In the initial state of Figure 12B(a), in Xcvr#2, the spectrum mx of Mx 133 is shifted toward the high frequency side, and the spectrum dmx of Dmx 141 is shifted toward the low frequency side, with the low frequency side of the spectrum of the optical signal (sig) being cut off by the low frequency end of mx. Also, in Xcvr#1, the spectrum mx of Mx 133 is shifted toward the low frequency side, and the spectrum dmx of Dmx 141 is shifted toward the high frequency side, with the low frequency side of the spectrum of sig being cut off by the low frequency end of dmx.

[0088] After the above control is performed, in the steady state shown in FIG. 12(b), the signal band of sig falls within the band where the spectrum mx of Mx 133 and the spectrum dmx of Dmx 141 overlap in both Xcvr#1 and Xcvr#2.

[0089] 13A and 13B are explanatory diagrams of the effects of the embodiment. FIG. 13A(a) is a chart similar to FIG. 5B(a), where the horizontal axis indicates frequency spacing offset (%) and the vertical axis indicates Q-factor penalty (dB). FIG. 13A(b) shows the band state of subcarrier N after control corresponding to the Mx / Dmx frequency spacing deviation according to the embodiment. In the embodiment, the transmission signal carrier spacing Δf r The channel frequency interval Δf tmx and the channel frequency interval Δf of the Dmx of the opposite receiver rdmx This controls the frequency band mx to the intermediate value of f mx(N) is located, and the middle value of the Dmx band dmx is f dmx(N) is located.

[0090] In reality, as shown in FIG. 13B, the signal spectrum is asymmetrically filtered by Mx / Dmx, but the effect was estimated assuming that the signal spectrum is approximately symmetrically filtered, including the state of FIG. 13B.

[0091] According to the embodiment, when compared with the conventional method using the same number of carriers, the difference between the carrier spacing and the Mx / Dmx channel frequency spacing is halved, improving the Q factor. For example, assuming the number of carriers N=16, the Q factor penalty can be improved by approximately 3 dB.

[0092] Furthermore, when there is a limit to the Q value, the difference between the carrier spacing and the Mx / Dmx channel frequency spacing is halved, making it possible to exceed the limit of the Q value. For example, as shown in Fig. 13A(a), whereas the upper limit on the number of subcarriers was previously N = 8, in the embodiment, the number of subcarriers can be increased (approximately doubled) to about N = 16.

[0093] (Other embodiments) In the above-described embodiment, the VCO 113 and phase modulator 112 inside one transceiver 100 are shared for both transmission and reception, but the other embodiment described below is an example of a configuration in which the VCO 113 and phase modulator 112 are provided separately for transmission and reception.

[0094] Fig. 14 is a diagram showing an example of the configuration of an optical transceiver according to another embodiment. In Fig. 14, the same components as those in Fig. 1 are denoted by the same reference numerals. In the example configuration shown in Fig. 14, a VCO 113t and a phase modulator 112t are arranged on the transmitting side, and a VCO 113r and a phase modulator 112r are arranged on the receiving side.

[0095] The controller (Ctrl) 120 performs the following controls 1 to 4. 1. The optical power (P mN ) to detect. 2. The current monitor value detected by the optical monitor 141d is compared with the previous monitor value, and the carrier interval Δf is adjusted so that the optical power detected by the optical monitor 141d becomes the maximum value. t1, Δf r1 Determine the direction of increase or decrease. 3. Determined carrier spacing Δf t1, Δf r1 The carrier interval Δf output by the phase modulator 112 of the transmitter 130 varies depending on the direction of increase or decrease oft1, Δf r1 is increased or decreased by a predetermined amount (δ). 4. As a result, the transmitter 130 receives the signal from the optical multiplexer (Mx) 133, which has a channel frequency interval Δf tmx1 The receiver 140 outputs an optical signal having a channel frequency interval Δf rdmx1 to the optical receiver 142.

[0096] (Example of control over the entire optical transmission system according to another embodiment) Fig. 15 is an explanatory diagram showing an example of control of the entire optical transmission system according to another embodiment. In Fig. 15, the same components as those in Fig. 14 are given the same reference numerals. An example of control performed in cooperation between the controllers 120, 120 of a pair of transceivers (Xcvr#1, Xcvr#2) in the transmission system will be described.

[0097] First, the controller (Ctrl) 120 of one transceiver (Xcvr#2) performs the following controls 1. to 3. 1. The optical power (P mN ) to detect. 2. The carrier interval Δf output by the phase modulator 112 of the transmitter 130 increases in the direction in which the current monitor value detected by the optical monitor 141d increases. t2, Δf r2 Control. 3. With the updated carrier spacing, the transmitter 130 determines whether the Mx 133 is in the channel frequency interval Δf tmx2 The optical signal having the above formula is transmitted and output to the optical transmission line 150b.

[0098] Next, the controller (Ctrl) 120 of the other transceiver (Xcvr#1) performs the following controls 4. to 6. 4. The optical power (P mN ) to detect. 5. The carrier interval Δf output by the phase modulator 112 of the transmitter 130 increases in the direction in which the current monitor value detected by the optical monitor 141d increases. t1, Δf r1 Control. 6. With the updated carrier interval, the transmitter 130 adjusts the channel frequency interval Δf tmx1 The optical signal having the above formula is transmitted and output to the optical transmission line 150a.

[0099] Fig. 16A is a sequence diagram of an example of control of the entire optical transmission system according to another embodiment. Fig. 16 shows the above-mentioned controls 1 to 6 of each controller (Ctrl) 120 of a pair of transceivers (Xcvr#1, Xcvr#2) in accordance with the control example of Fig. 15.

[0100] 16B is a diagram showing an example of VCO frequency control according to another embodiment. 16(a) to 16(f) show the optical signals Tx to be transmitted and Rx to be received based on the frequency setting change of each VCO 113 (113t, 113r), and the channel frequency interval Δf tmx1 , Δf tmx2 , the receiving channel frequency interval Δf rdmx1 , Δf rdmx2 The change in frequency (horizontal axis) is shown as a vertical position.

[0101] In the initial state of control shown in FIG. 16A, the filters Mx 133 and Dmx 141 and the center frequency of the laser light source 111 are the same (FIG. 16B(a)). In the initial state (0), the transceiver Xcvr#1 adjusts the carrier interval Δf of the optical signal Tx1 on the transmitting side. t1 (0), channel frequency interval Δf tmx1 , the carrier spacing Δf of the optical signal Rx1 on the receiving side r1 (0), channel frequency interval Δf rdmx1 The transceiver Xcvr#2 transmits the optical signal Tx2 with a carrier spacing Δf t2 (0), channel frequency interval Δf tmx2 , the carrier spacing Δf of the optical signal Rx2 on the receiving side r2 (0), channel frequency interval Δf rdmx2 is.

[0102] Then, during the first (1) adjustment control, the transceiver Xcvr#1 transmits an optical signal (data transfer). As a result, the transceiver Xcvr#2: 1. The optical monitor 141d of the Dmx 141 of the receiver 140 detects the optical power (P mN ) is detected. Next, 2. The carrier interval Δf output from the phase modulator 112r via its own VCO 113r is detected in the direction in which the current monitor value detected by the optical monitor 141d increases. r2 By implementing the control corresponding to the frequency interval deviation, the channel frequency interval Δf is adjusted by the adjustment amount δ as shown in FIG. 16B(b). rdmx2 3. The transmitter 130 changes the channel frequency interval Δf rdmx2 and correspondingly, the transceiver Xcvr#1 transmits Tx2 to the transceiver Xcvr#1 at a channel frequency interval Δf rdmx1 (1) Rx1 is received (FIG. 16B(b)).

[0103] New channel frequency interval Δf rdmx2 In accordance with (1), the transmitter 130 transmits Tx2 via the VCO 113t by the phase modulator 112t at a channel frequency interval Δf tmx2 Change to (1) (Rx2=Tx2, Figure 16B(d)).

[0104] 4. The transceiver Xcvr#1 measures the optical power (P mN ) is detected. 5. The carrier interval Δf of the receiver 140 itself is detected in the direction in which the current monitor value detected by the optical monitor 141d increases. r1 By implementing control to deal with the frequency spacing difference, Rx1 controls the channel frequency spacing Δf rdmx1 (1) (Figure 16B(c)).

[0105] New channel frequency interval Δf rdmx1 In accordance with (1), the transmitter 130 transmits Tx1 via the VCO 113t by the phase modulator 112t at a channel frequency interval Δf tmx1Change to (1) (Rx1=Tx1, Figure 16B(e)).

[0106] After this, during the second (2) adjustment control, the transceiver Xcvr#1 adjusts the channel frequency interval Δf tmx1 Tx1 having (1) is transmitted and output to the optical transmission line 150a.

[0107] Thereafter, the controllers (Ctrl) 120 of the pair of transceivers (Xcvr#1, Xcvr#2) repeatedly execute the above-described controls 1 to 6. By the above-described control for reducing the difference between the carrier interval and the channel frequency interval, the channel frequency interval Δf rdmx2 ,Δf rdmx1 can be gradually brought closer.

[0108] According to the other embodiment described above, the VCO 113 and the phase modulator 112 are respectively provided in the transmitter 130 and the receiver 140. This makes it possible to reduce the difference between the carrier spacing and the channel frequency spacing depending on the MX / Dmx error between the transmitting and receiving sides.

[0109] The optical transceiver according to the above-described embodiment includes a multi-wavelength light source that outputs light of multiple optical frequencies with a predetermined carrier spacing, a transmitter, a receiver, and a controller. The transmitter includes multiple optical modulators that generate optical signals by optically modulating the multiple light beams output from the multi-wavelength light source based on data, and an optical multiplexer that combines the optical signals output from the multiple optical modulators with a predetermined channel frequency spacing and outputs the combined optical signals to a transmission optical transmission path. The receiver includes an optical demultiplexer that demultiplexes the optical signal from the reception optical transmission path into multiple optical signals with a predetermined channel frequency spacing, and multiple optical receivers that coherently detect each of the multiple optical signals output by the optical demultiplexer using light from the multi-wavelength light source and demodulate the data. The controller controls the carrier spacing output from the multi-wavelength light source based on the optical power of the optical signals output by the optical demultiplexer of the receiver, and adjusts the channel frequency spacing output by the optical multiplexer of the transmitter relative to the carrier spacing. Optical multiplexers and optical demultiplexers have different filter characteristics due to manufacturing reasons, and there is an initial discrepancy between the carrier spacing and the channel frequency spacing. However, by using the above control, it is possible to suppress the discrepancy between the carrier spacing and the channel frequency spacing output by the transmitter's optical multiplexer, and to optimally adjust the spacing between multiple optical frequencies for optical transmission.

[0110] In addition, in the optical transceiver according to the embodiment, the controller may control the carrier spacing to be an intermediate value between the channel frequency spacing of the optical multiplexer of the transmitter and the channel frequency spacing of the optical demultiplexer of the receiver, thereby suppressing the spectral components of the optical signal that are cut off by the filter characteristics of the optical demultiplexer and improving transmission characteristics such as the Q factor.

[0111] In addition, in the optical transceiver according to the embodiment, the demultiplexer may have an optical monitor that detects the optical power of an output port at which the center frequency of the optical spectrum of the plurality of optical signals is maximized or minimized, and the controller may perform control to increase or decrease the carrier spacing so that the optical power detected by the optical monitor is maximized. For example, by providing one optical monitor at the outermost output port of a signal band where the greatest frequency deviation error occurs, it becomes possible to easily and efficiently adjust the plurality of optical frequency spacings.

[0112] In addition, in the optical transceiver according to the embodiment, the controller may compare the current output power of the optical monitor with the previous output power, and based on the comparison result, control the direction of increase / decrease in the carrier spacing relative to the frequency and the amount of adjustment. The control by the controller can be performed over time during optical transmission operation, allowing the spacing between multiple optical frequencies to be optically transmitted to always be optimally maintained.

[0113] Furthermore, the optical transceiver of the embodiment may use an optical multiplexer and an optical demultiplexer formed on the same optical chip, which allows the filter characteristics of the optical multiplexer and the optical demultiplexer to be nearly identical, thereby improving the accuracy of adjustment.

[0114] Furthermore, in the optical transceiver according to the embodiment, the multi-wavelength light source can take various forms. For example, the multi-wavelength light source can include a light source that outputs light, e.g., continuous light, a phase modulator that receives light from the light source and outputs light of multiple optical frequencies based on the control voltage of the voltage-controlled oscillator, and a voltage-controlled oscillator. In this case, the transmitter includes an optical demultiplexer that demultiplexes the light of multiple optical frequencies output by the phase modulator to multiple optical modulators, and the receiver includes an optical demultiplexer that demultiplexes the light of multiple optical frequencies output by the phase modulator to multiple optical receiving units. Alternatively, the multi-wavelength light source can be an array light source that outputs light of multiple frequencies. In this case, the light of the array light source at multiple frequencies can be directly output to multiple optical modulators and optical receivers, eliminating the need for an optical demultiplexer.

[0115] In addition, in the optical transceiver of the embodiment, the transmitter and receiver may each have a phase modulator and a voltage-controlled oscillator, which can reduce the difference between the carrier spacing and the channel frequency spacing depending on the MX / Dmx error between the transmitter and receiver.

[0116] The optical transmission system according to the embodiment can be configured with a pair of optical transceivers facing each other via a transmission line. In this case, each optical transceiver can control the carrier spacing in its own device based on the optical signals transmitted and received by the other.

[0117] The following additional notes are provided regarding the above-described embodiment.

[0118] (Supplementary Note 1) A multi-wavelength light source that outputs light of a plurality of optical frequencies having a predetermined carrier interval, a transmitter, a receiver, and a controller, The transmitter a plurality of optical modulators that generate optical signals by optically modulating the plurality of light beams output from the multi-wavelength light source based on data; an optical multiplexer that multiplexes optical signals output from the plurality of optical modulators at a predetermined channel frequency interval and outputs the multiplexed optical signals to a transmission optical transmission path; The receiver includes: an optical demultiplexer that demultiplexes an optical signal on a receiving optical transmission line into a plurality of optical signals having a predetermined channel frequency interval; a plurality of optical receivers that coherently detect the plurality of optical signals output by the optical demultiplexer using light from the multi-wavelength light source and demodulate the data, The controller controlling the carrier spacing output from the multi-wavelength light source based on the optical power of the optical signal output from the optical demultiplexer of the receiver, and adjusting the channel frequency spacing output from the optical multiplexer of the transmitter relative to the carrier spacing; An optical transceiver characterized by:

[0119] (Supplementary Note 2) The controller The optical transceiver described in Supplementary Note 1, characterized in that the carrier spacing is controlled to be an intermediate value between the channel frequency spacing of the optical multiplexer of the transmitter and the channel frequency spacing of the optical demultiplexer of the receiver.

[0120] (Supplementary Note 3) The duplexer is an optical monitor for detecting the optical power of an output port at which the center frequency of the optical spectrum of a plurality of optical signals is maximum or minimum; The controller 2. The optical transceiver according to claim 1, wherein the carrier spacing is controlled to be increased or decreased so that the optical power detected by the optical monitor is maximized.

[0121] (Supplementary Note 4) The controller The optical transceiver described in Appendix 3, characterized in that the current output power of the optical monitor is compared with the previous output power, and the direction of increase / decrease in the carrier spacing relative to the frequency and the amount of adjustment are controlled based on the comparison result.

[0122] (Appendix 5) The optical transceiver according to appendix 1, wherein the optical multiplexer and the optical demultiplexer are formed on the same optical chip.

[0123] (Supplementary Note 6) The multi-wavelength light source is a light source that outputs light; a phase modulator that receives light from the light source and outputs light of the plurality of optical frequencies based on the control voltage of the voltage-controlled oscillator; a voltage-controlled oscillator; The transmitter an optical demultiplexer that demultiplexes and outputs the light of the plurality of optical frequencies output by the phase modulator to the plurality of optical modulators, The receiver includes: an optical demultiplexer that demultiplexes and outputs the light of the plurality of optical frequencies output by the phase modulator to the plurality of optical receiving units; 2. The optical transceiver of claim 1, comprising:

[0124] (Supplementary Note 7) The multi-wavelength light source is a light source that outputs light; a phase modulator for a transmitter that receives light from the light source and outputs light of the plurality of optical frequencies based on a control voltage of the voltage-controlled oscillator; a voltage-controlled oscillator for the transmitter; a phase modulator for a receiver that receives light from the light source and outputs light of the plurality of optical frequencies based on a control voltage of the voltage-controlled oscillator; a voltage-controlled oscillator for the receiver; The transmitter an optical demultiplexer that demultiplexes and outputs the light of the plurality of optical frequencies output by the phase modulator for the transmitter to the plurality of optical modulators; The receiver includes: an optical demultiplexer that demultiplexes the light of the plurality of optical frequencies output by the receiver phase modulator and outputs the demultiplexed light to the plurality of optical receiving units; 2. The optical transceiver of claim 1, comprising:

[0125] (Appendix 8) In an optical transmission system having a pair of optical transceivers facing each other via an optical transmission line, Each of the pair of optical transceivers comprises: The optical fiber includes a multi-wavelength light source that outputs light of a plurality of optical frequencies having a predetermined carrier interval, a transmitter, a receiver, and a controller; The transmitter a plurality of optical modulators that generate optical signals by optically modulating the plurality of light beams output from the multi-wavelength light source based on data; an optical multiplexer that multiplexes optical signals output from the plurality of optical modulators at a predetermined channel frequency interval and outputs the multiplexed optical signals to a transmission optical transmission path; The receiver includes: an optical demultiplexer that demultiplexes an optical signal on a receiving optical transmission line into a plurality of optical signals having a predetermined channel frequency interval; a plurality of optical receivers that coherently detect the plurality of optical signals output by the optical demultiplexer using light from the multi-wavelength light source and demodulate the data, The controller transmitting and receiving the optical signal between the opposing optical transceiver, and controlling the carrier spacing output by the multi-wavelength light source in the optical transceiver based on the optical power of the optical signal output by the optical demultiplexer of the receiver, and adjusting the channel frequency spacing output by the optical multiplexer of the transmitter relative to the carrier spacing; An optical transmission system comprising:

[0126] (Supplementary Note 9) A multi-wavelength light source that outputs light of a plurality of optical frequencies having a predetermined carrier interval, a transmitter, a receiver, and a controller, The transmitter a plurality of optical modulators that generate optical signals by optically modulating the plurality of light beams output from the multi-wavelength light source based on data; an optical multiplexer that multiplexes optical signals output from the plurality of optical modulators at a predetermined channel frequency interval and outputs the multiplexed optical signals to a transmission optical transmission path; The receiver includes: an optical demultiplexer that demultiplexes an optical signal on a receiving optical transmission line into a plurality of optical signals having a predetermined channel frequency interval; a plurality of optical receivers that coherently detect the plurality of optical signals output by the optical demultiplexer using light from the multi-wavelength light source and demodulate the data, The controller controlling the carrier spacing output from the multi-wavelength light source based on the optical power of the optical signal output from the optical demultiplexer of the receiver, and adjusting the channel frequency spacing output from the optical multiplexer of the transmitter relative to the carrier spacing; 2. A carrier spacing control method for an optical transceiver, comprising:

[0127] (Supplementary Note 10) The controller 10. The carrier spacing control method for an optical transceiver described in claim 9, wherein the carrier spacing is controlled to be an intermediate value between the channel frequency spacing of the optical multiplexer of the transmitter and the channel frequency spacing of the optical demultiplexer of the receiver. [Explanation of symbols]

[0128] 100 Optical Transceiver (Transceiver) 101 Multi-wavelength light source 111 Laser light source 112 Phase Modulator 113 VCO 120 Controller 130 Transmitter 131,141,143 Optical demultiplexer (Dmx) 132 Optical Modulator 140 Receiver 141d Optical Monitor 142 Optical Receiver 150 Optical transmission line 801 processor 802 memory 805 Recording Media NW Network Tx,Rx(sig) Optical signal Δf r ,Δf t Carrier Spacing Δf tmx ,Δf rdmx Channel Frequency Spacing

Claims

1. The optical fiber includes a multi-wavelength light source that outputs light of a plurality of optical frequencies having a predetermined carrier interval, a transmitter, a receiver, and a controller; The transmitter a plurality of optical modulators that generate optical signals by optically modulating the plurality of light beams output from the multi-wavelength light source based on data; an optical multiplexer that multiplexes optical signals output from the plurality of optical modulators at a predetermined channel frequency interval and outputs the multiplexed optical signals to a transmission optical transmission path; The receiver includes: an optical demultiplexer that demultiplexes an optical signal on a receiving optical transmission line into a plurality of optical signals having a predetermined channel frequency interval; a plurality of optical receivers that coherently detect the plurality of optical signals output by the optical demultiplexer using light from the multi-wavelength light source and demodulate the data, The controller controlling the carrier spacing output by the multi-wavelength light source based on the optical power of the optical signal output by the optical demultiplexer of the receiver, and adjusting the channel frequency spacing output by the optical multiplexer of the transmitter relative to the carrier spacing; An optical transceiver characterized by:

2. The controller 2. The optical transceiver according to claim 1, wherein the carrier spacing is controlled to be an intermediate value between the channel frequency spacing of the optical multiplexer of the transmitter and the channel frequency spacing of the optical demultiplexer of the receiver.

3. The duplexer comprises: an optical monitor for detecting the optical power of an output port at which the center frequency of the optical spectrum of a plurality of optical signals is maximum or minimum; The controller 2. The optical transceiver according to claim 1, wherein the carrier interval is controlled to be increased or decreased so that the optical power detected by the optical monitor is maximized.

4. The controller 4. The optical transceiver according to claim 3, wherein the current output power of the optical monitor is compared with the previous output power, and the direction and amount of increase / decrease of the carrier spacing relative to the frequency are controlled based on the comparison result.

5. 2. The optical transceiver according to claim 1, wherein the optical multiplexer and the optical demultiplexer are formed on the same optical chip.

6. The multi-wavelength light source is a light source that outputs light; a phase modulator that receives light from the light source and outputs light of the plurality of optical frequencies based on the control voltage of the voltage-controlled oscillator; a voltage-controlled oscillator; The transmitter an optical demultiplexer that demultiplexes and outputs the light of the plurality of optical frequencies output by the phase modulator to the plurality of optical modulators, The receiver includes: an optical demultiplexer that demultiplexes and outputs the light of the plurality of optical frequencies output by the phase modulator to the plurality of optical receiving units; 2. The optical transceiver according to claim 1, further comprising:

7. The multi-wavelength light source is a light source that outputs light; a phase modulator for a transmitter that receives light from the light source and outputs light of the plurality of optical frequencies based on a control voltage of the voltage-controlled oscillator; a voltage-controlled oscillator for the transmitter; a phase modulator for a receiver that receives light from the light source and outputs light of the plurality of optical frequencies based on a control voltage of the voltage-controlled oscillator; a voltage-controlled oscillator for the receiver; The transmitter an optical demultiplexer that demultiplexes and outputs the light of the plurality of optical frequencies output by the phase modulator for the transmitter to the plurality of optical modulators, The receiver includes: an optical demultiplexer that demultiplexes the light of the plurality of optical frequencies output by the receiver phase modulator and outputs the demultiplexed light to the plurality of optical receiving units; 2. The optical transceiver according to claim 1, further comprising:

8. In an optical transmission system having a pair of optical transceivers facing each other via an optical transmission line, Each of the pair of optical transceivers comprises: The optical fiber includes a multi-wavelength light source that outputs light of a plurality of optical frequencies having a predetermined carrier interval, a transmitter, a receiver, and a controller; The transmitter a plurality of optical modulators that generate optical signals by optically modulating the plurality of light beams output from the multi-wavelength light source based on data; an optical multiplexer that multiplexes optical signals output from the plurality of optical modulators at a predetermined channel frequency interval and outputs the multiplexed optical signals to a transmission optical transmission path; The receiver includes: an optical demultiplexer that demultiplexes an optical signal on a receiving optical transmission line into a plurality of optical signals having a predetermined channel frequency interval; a plurality of optical receivers that coherently detect the plurality of optical signals output by the optical demultiplexer using light from the multi-wavelength light source and demodulate the data, The controller transmitting and receiving the optical signal between the opposing optical transceiver, and controlling the carrier spacing output by the multi-wavelength light source in the optical transceiver based on the optical power of the optical signal output by the optical demultiplexer of the receiver, and adjusting the channel frequency spacing output by the optical multiplexer of the transmitter relative to the carrier spacing; An optical transmission system comprising:

9. The optical fiber includes a multi-wavelength light source that outputs light of a plurality of optical frequencies having a predetermined carrier interval, a transmitter, a receiver, and a controller; The transmitter a plurality of optical modulators that generate optical signals by optically modulating the plurality of light beams output from the multi-wavelength light source based on data; an optical multiplexer that multiplexes optical signals output from the plurality of optical modulators at a predetermined channel frequency interval and outputs the multiplexed optical signals to a transmission optical transmission path; The receiver includes: an optical demultiplexer that demultiplexes an optical signal on a receiving optical transmission line into a plurality of optical signals having a predetermined channel frequency interval; a plurality of optical receivers that coherently detect the plurality of optical signals output by the optical demultiplexer using light from the multi-wavelength light source and demodulate the data, The controller controlling the carrier spacing output by the multi-wavelength light source based on the optical power of the optical signal output by the optical demultiplexer of the receiver, and adjusting the channel frequency spacing output by the optical multiplexer of the transmitter relative to the carrier spacing; 2. A carrier spacing control method for an optical transceiver, comprising:

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