JP2005027196A - Crosstalk elimination method, crosstalk elimination circuit, optical transceiver, and optical transmission system - Google Patents

Abstract

An optical crosstalk in which a receiving circuit of a local station receives a part of an optical signal output from a light emitting element of the local station and an electric signal in which a part of an electrical data signal transmitted by the local station interferes with the receiving circuit of the local station. Provided are a crosstalk elimination method, a crosstalk elimination circuit, an optical transmission / reception apparatus, and an optical transmission system, in which degradation of reception characteristics due to crosstalk is suppressed.
A buffer circuit for branching an input electrical data signal, a frequency characteristic adjusting circuit for adjusting a frequency characteristic of one output signal of the buffer circuit, and an amplitude level of an output signal of the frequency characteristic adjusting circuit are adjusted. A crosstalk removing circuit 17 having an amplitude adjusting circuit 8 for subtracting, and a subtracting circuit 11 for subtracting an output signal of the amplitude adjusting circuit from an electric signal obtained by converting an optical signal inputted from the transmission optical fiber 16.
[Selection] Figure 1

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical transceiver that converts an input electrical signal into an optical signal and outputs the optical signal to a transmission optical fiber, and converts the optical signal input from the transmission optical fiber into an electrical signal and outputs the electrical signal. In particular, optical crosstalk in which an optical signal to be transmitted leaks to an optical signal to be received and electrical crosstalk in which an electrical signal interferes with a peripheral circuit when an electrical data signal is converted into an optical signal and transmitted are removed. The present invention relates to a crosstalk removing method, a crosstalk removing circuit, and an optical transmission / reception apparatus and an optical transmission system including the crosstalk removing circuit.
[0002]
[Prior art]
FIG. 6 is a block diagram showing a conventional optical transmitter / receiver (see, for example, Patent Document 1 below). As shown in FIG. 6, a conventional optical transceiver 26 includes a light emitting element 1 that converts an input electric signal into an optical signal, a light receiving element 2 that converts an input optical signal into an electric signal, and the weakness of the light receiving element 2. An optical module 5 including a preamplifier 4 for amplifying a low output electric signal, a light emitting element 1, a transmission optical fiber 16 and a wavelength demultiplexing element 3 optically coupled to the light receiving element 2, and the optical module 5 And a driving circuit 6 for driving the light emitting element 1.
[0003]
[Patent Document 1]
Japanese Patent No. 3006004 [0004]
Further, the optical transmitter / receiver 26 branches the input electrical data signal and outputs a normal phase output that is output to the drive circuit 6 and a reverse phase output that is an output of the opposite phase to that of the buffer circuit 7 and the reverse of the buffer circuit 7. An amplitude adjustment circuit 8 for attenuating and adjusting the output amplitude of the phase output and subtracting it from the output of the preamplifier 4, a phase adjustment circuit 10, and a crosstalk elimination circuit 25 comprising a subtraction circuit 11 are provided.
[0005]
Further, the optical transmitter / receiver 26 controls the amplitude of the electric signal output from the preamplifier 4 of the optical module 5 from which the crosstalk has been subtracted via the subtracting circuit 11 to be constant, and outputs the AGC amplifier 12 and the AGC amplifier 12. A clock recovery circuit 13 that extracts and reproduces a clock component from the electrical signal output from the AGC amplifier, and a data recovery circuit 14 that recovers a data signal using the clock signal output from the clock recovery circuit 13 from the electrical signal output from the AGC amplifier 12. It has.
[0006]
Here, when the electric signal input to the drive circuit 6 is at a high level, the output of the preamplifier 4 is also at a level corresponding to the high level. When this relationship is reversed, the input to the phase adjustment circuit 10 branches the normal phase output of the buffer circuit 7 into two branches, or an inverting buffer circuit (not shown) is inserted into the negative phase output of the buffer circuit 7 and the phase is shifted. Input to the adjustment circuit 10.
[0007]
The electrical data signal input to the optical transmitter / receiver 26 is branched into two by the buffer circuit 7, and one positive phase output is input to the drive circuit 6. The light emitting element 1 is driven by the drive circuit 6 to be converted into an optical signal, and is input to the transmission optical fiber 16 through the wavelength multiplexing / demultiplexing element 3 operating as a coupling / branching device and transmitted as an optical signal. On the other hand, an optical signal input from the transmission optical fiber 16 is input to the light receiving element 2 via the wavelength demultiplexing element 3 and amplified by the preamplifier 4 with low noise.
[0008]
Here, the signal transmitted by the own station is also output together with the optical crosstalk represented by the solid arrow in FIG. 6 and the electrical crosstalk represented by the dotted arrow. The other antiphase output of the buffer circuit 7 is adjusted by the phase adjustment circuit 10 so that it is in phase with the crosstalk contained in the output of the preamplifier 4, and the optical crosstalk level and the electric crosstalk are adjusted by the amplitude adjustment circuit 8. It is adjusted to be equal to the sum of levels. For this reason, when the signal output from the amplitude adjustment circuit 8 is subtracted from the output of the preamplifier 4 by the subtraction circuit 11, the crosstalk transmitted by the own station is canceled by the output of the amplitude adjustment circuit 8 and output to the AGC amplifier 12. This signal is amplified by the AGC amplifier 12, and the data signal and the clock signal are reproduced and output by the clock reproduction circuit 13 and the data reproduction circuit 14.
[0009]
As described above, even in the conventional optical transmission / reception apparatus, the crosstalk is subtracted from the input optical signal, the data signal and the clock signal are reproduced and output, and the input electrical data signal is converted into the optical signal and output. In addition, single-core bidirectional optical communication in which optical signals for transmission and reception are exchanged with a single-core transmission optical fiber can be realized.
[0010]
[Problems to be solved by the invention]
However, in the conventional optical transceiver, a part of the optical signal output from the light emitting element 1 in the optical module 5 of FIG. 6 is input to the light receiving element 2 (indicated by the solid arrow in FIG. 6). In addition to the crosstalk, an electrical signal before being input to the light emitting element 1 interferes with the preamplifier 4 and peripheral circuit patterns (indicated by dotted arrows in FIG. 6). 7 and 8 show the frequency characteristics of optical crosstalk and electrical crosstalk, respectively. Electrical crosstalk often occurs due to capacitive coupling, and the amplitude increases as the frequency increases as shown in FIG. As the transmission / reception signal has higher frequency characteristics, the influence of electrical crosstalk becomes larger than that of optical crosstalk, and the influence of frequency characteristics shown in FIG. was there.
[0011]
The present invention has been made to solve the above-described conventional problems, and includes a crosstalk removal method, a crosstalk removal circuit, and such a crosstalk removal circuit that removes a crosstalk signal to obtain excellent reception characteristics. Another object of the present invention is to provide an optical transmitter / receiver and an optical transmitter / receiver system.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, a crosstalk elimination method according to the present invention branches an inputted electrical data signal into two, converts one branched electrical data signal into an optical signal, transmits it, and branches The frequency of the other electrical data signal is adjusted by a frequency characteristic adjustment circuit having a frequency characteristic substantially equal to the frequency characteristic of the electrical crosstalk, and the frequency is adjusted from the electric signal obtained by converting the optical signal received via the optical fiber. By subtracting the electrical signal, the electrical crosstalk in which the transmission signal leaks into the reception signal is removed. By this method, the electric crosstalk signal can be removed.
[0013]
In the crosstalk elimination method according to the present invention, an input electrical data signal is branched into two, one branched electrical data signal is converted into an optical signal and transmitted, and the other branched electrical data is transmitted. The frequency of the signal is adjusted by a frequency characteristic adjustment circuit having a frequency characteristic substantially equal to the frequency characteristic of optical crosstalk, and the frequency adjusted electric signal is subtracted from the electric signal obtained by converting the optical signal received through the optical fiber. The optical crosstalk in which the transmission signal leaks into the reception signal is removed. By this method, the optical crosstalk signal can be more accurately removed.
[0014]
The crosstalk elimination circuit according to the present invention includes a branch circuit that branches an input electrical data signal, a frequency characteristic adjustment circuit that adjusts a frequency characteristic of one output signal of the branch circuit, and the frequency characteristic adjustment circuit. An amplitude adjustment circuit for adjusting the amplitude level of the output signal, and a subtraction circuit for subtracting the output signal of the amplitude adjustment circuit from an electrical signal obtained by converting the optical signal input from the optical fiber. With this configuration, the crosstalk signal is removed. This also makes it possible to provide an optical transmission / reception apparatus with a small number of crosstalk signals.
[0015]
The frequency characteristic adjusting circuit has a frequency characteristic substantially equal to a frequency characteristic of electrical crosstalk. With this configuration, the electrical crosstalk signal can be removed. For this reason, it is possible to provide an optical transmission / reception apparatus with few crosstalk signals.
[0016]
The frequency characteristic adjusting circuit has a frequency characteristic substantially equal to the frequency characteristic of the optical black stroke. With this configuration, the optical crosstalk signal can be more accurately removed. For this reason, it is possible to provide an optical transmission / reception apparatus with few crosstalk signals.
[0017]
The branch circuit is a buffer circuit that inputs an electric signal and sends out a normal phase output and a negative phase output, and the frequency characteristic adjustment circuit is a high-frequency component that passes a high-frequency component of the negative phase output of the buffer circuit. It is a band-pass filter, and the amplitude adjustment circuit is a resistance element. With this configuration, the frequency amplitude characteristic of the electrical crosstalk signal can be corrected and removed. For this reason, it is possible to provide an optical transmission / reception apparatus with fewer electrical crosstalk signals.
[0018]
The branch circuit is a buffer circuit that inputs an electric signal and sends out a normal phase output and a negative phase output, and the frequency characteristic adjustment circuit is a low-frequency component that passes a low-frequency component of the negative phase output of the buffer circuit. It is a band-pass filter, and the amplitude adjustment circuit is a resistance element. With this configuration, the frequency amplitude characteristic of the optical crosstalk signal can be corrected and removed. For this reason, it is possible to provide an optical transmission / reception apparatus with fewer optical crosstalk signals.
[0019]
Further, the crosstalk removing circuit described above further includes a phase adjusting circuit for adjusting the phase of a signal whose frequency characteristics are adjusted. With this configuration, the phase and frequency characteristics can be adjusted together. For this reason, it is possible to provide an optical transmission / reception apparatus with fewer crosstalk signals.
[0020]
Further, the present invention is characterized by comprising the above-described crosstalk removing circuit for removing the electrical crosstalk and the above-described crosstalk removing circuit for removing the optical crosstalk. With this configuration, the optical crosstalk signal and the electrical crosstalk signal can be individually removed. For this reason, it is possible to provide an optical transmission / reception apparatus with fewer crosstalk signals.
[0021]
The optical transmission / reception apparatus according to the present invention includes the crosstalk elimination circuit described above, a drive circuit that inputs the other output signal of the branch circuit, and a light emission that is driven based on the output of the drive circuit and outputs an optical signal. An optical transmitter having an element, a light receiving element that receives an optical signal output from the light emitting element and an optical signal input from a transmission optical fiber, and converts the optical signal into an electrical signal; and amplifies the output of the light receiving element An optical receiver having a preamplifier; an amplifier for amplifying a signal obtained by subtracting the output of the amplitude adjusting circuit from the output of the optical receiver by the subtractor; and a data signal and a clock signal from the output signal of the amplifier And an electric circuit to be regenerated. With this configuration, it is possible to provide an optical transmission / reception apparatus that eliminates crosstalk signals and has good reception characteristics.
[0022]
Furthermore, the optical transmission system according to the present invention includes, as the above-described optical transmission / reception apparatus, two optical transmission / reception apparatuses having different wavelengths of an optical signal to be transmitted and an optical signal to be received, and the two optical transmission / reception apparatuses are connected by an optical fiber. And facing each other. With this configuration, it is possible to provide a single-core bidirectional optical transmission system capable of long-distance transmission using an optical transmission / reception apparatus including a crosstalk removal circuit.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
FIG. 1 is a block diagram showing an optical transceiver according to the first embodiment of the present invention. As shown in FIG. 1, an optical transceiver 15 according to a first embodiment of the present invention converts a light-emitting element 1 that converts an input electric signal into an optical signal, and converts an input optical signal into an electric signal. The light receiving element 2, the preamplifier 4 that amplifies a weak output electric signal of the light receiving element 2 with low noise, and the optical signal output from the light emitting element 1 are optically coupled to the transmission optical fiber 16 and input from the transmission optical fiber 16. The optical module 5 includes a wavelength demultiplexing element 3 that optically couples the optical signal to the light receiving element 2.
[0024]
The optical transceiver 15 also includes a drive circuit 6 for driving the light emitting element 1 of the optical module 5, a normal-phase output that branches an input electrical data signal and outputs it to the drive circuit 6, and an output in the opposite phase thereof. A crosstalk removal circuit 17 configured by a buffer circuit 7 that sends a reverse phase output, an amplitude adjustment circuit 8, a frequency characteristic adjustment circuit 9, a phase adjustment circuit 10 and a subtraction circuit 11, and a crosstalk via the subtraction circuit 11. Are subtracted from the preamplifier 4 of the optical module 5 so that the amplitude of the electrical signal output from the preamplifier 4 is controlled to be constant, and the clock recovery circuit 13 extracts the clock component from the electrical signal output from the AGC amplifier 12 and reproduces it. And a data recovery circuit for recovering the data signal from the electrical signal output from the AGC amplifier 12 using the clock signal output from the clock recovery circuit 13. And a 14.
[0025]
Here, when the electric signal input to the drive circuit 6 is at a high level, the output of the preamplifier 4 is also at a level corresponding to the high level. When this relationship is reversed, the input to the phase adjustment circuit 10 branches the normal phase output of the buffer circuit 7 into two branches, or an inverting buffer circuit (not shown) is inserted into the negative phase output of the buffer circuit 7 and the phase is shifted. Input to the adjustment circuit 10.
[0026]
The amplitude adjustment circuit 8 attenuates and adjusts the output amplitude of the reverse phase output of the buffer circuit 7, and the subtraction circuit 11 subtracts the output of the amplitude adjustment circuit 8 from the output of the preamplifier 4.
The frequency characteristic adjusting circuit 9 is set so as to be a capacitively coupled high-pass filter, that is, to have a frequency characteristic of electric crosstalk because electric crosstalk occurs due to spatial coupling. It has the characteristics shown. In the phase adjustment circuit 10, the positive phase output of the buffer circuit 7 is input to the drive circuit 6, and is adjusted to a phase that is output to the preamplifier 4 as electric crosstalk. Note that the AGC amplifier 12 may be a limiting amplifier with a wide dynamic range that outputs the signal by limiting the amplitude of the input signal. The amplitude adjustment circuit 8 may be a resistance element.
[0027]
The operation of the optical transceiver configured as above will be described. First, the electrical signal input to the optical transceiver 15 is branched into two by the buffer circuit 7, and one positive phase output is input to the drive circuit 6. The light emitting element 1 is driven by the drive circuit 6, so that the electric signal is converted into an optical signal, input to the transmission optical fiber 16 through the wavelength multiplexing / demultiplexing element 3, and transmitted as an optical signal. An optical signal input from the transmission optical fiber 16 is input to the light receiving element 2 through the wavelength demultiplexing element 3 and amplified by the preamplifier 4 with low noise.
[0028]
Here, the signal transmitted by the own station is also output together with the optical crosstalk represented by the solid arrow in FIG. 1 and the electrical crosstalk represented by the dotted arrow. The other antiphase output of the buffer circuit 7 is adjusted by the phase adjustment circuit 10, the frequency characteristic adjustment circuit 9 and the amplitude adjustment circuit 8 so that the phase of the electrical crosstalk level is canceled and the frequency characteristic and the amplitude become equal. . Therefore, when the output of the amplitude adjustment circuit 8 is subtracted from the output of the preamplifier 4 by the subtraction circuit 11, the crosstalk transmitted by the own station is canceled by the output of the amplitude adjustment circuit 8 and output to the AGC amplifier 12. This signal is amplified by the AGC amplifier 12, and the data signal and the clock signal are reproduced and output by the clock reproduction circuit 13 and the data reproduction circuit 14.
[0029]
Therefore, according to the optical transmission / reception apparatus of the first embodiment of the present invention, the data signal transmitted by the local station is branched into two in advance, and the phase is adjusted by the phase adjustment circuit 10, the frequency characteristic adjustment circuit 9, and the amplitude adjustment circuit 8. After adjusting the frequency characteristics and amplitude, and subtracting from the received signal, the electrical crosstalk component that degrades the reception characteristics can be removed, so that the optical transmission / reception apparatus for a single-core bidirectional optical communication system having excellent reception characteristics Can be provided.
[0030]
<Second Embodiment>
FIG. 3 is a frequency characteristic diagram of the frequency adjustment circuit 9 according to the second embodiment of the present invention. The optical transmission / reception apparatus according to the second embodiment of the present invention has the same configuration as that of the first embodiment shown in FIG. 1 and the frequency characteristics of the frequency characteristic adjustment circuit 9 are different. The frequency characteristic adjusting circuit 9 of the second embodiment is a low-pass filter that is substantially equal to the frequency characteristic of the drive circuit 6, the light emitting element 1, the light receiving element 2, and the preamplifier 4, that is, the optical crosstalk frequency characteristic. And has the characteristics shown in FIG. The amplitude adjustment circuit 8 may be a resistance element.
[0031]
The operation of the optical transceiver configured as above will be described. First, the electrical signal input to the optical transceiver 15 is branched into two by the buffer circuit 7, and one positive phase output is input to the drive circuit 6. The light emitting element 1 is driven by the drive circuit 6 to be converted into an optical signal, input to the transmission optical fiber 16 through the wavelength multiplexing / demultiplexing element 3, and transmitted as an optical signal. An optical signal input from the transmission optical fiber 16 is input to the light receiving element 2 through the wavelength demultiplexing element 3 and amplified by the preamplifier 4 with low noise.
[0032]
Here, the signal transmitted by the own station is also output together with the optical crosstalk represented by the solid arrow in FIG. 1 and the electrical crosstalk represented by the dotted arrow. The other antiphase output of the buffer circuit 7 is adjusted by the phase adjustment circuit 10, the frequency characteristic adjustment circuit 9 and the amplitude adjustment circuit 8 so that the phase of the optical crosstalk level is canceled and the frequency characteristic and the amplitude become equal. Yes. Therefore, when the output of the amplitude adjustment circuit 8 is subtracted from the output of the preamplifier 4 by the subtraction circuit 11, the crosstalk transmitted by the own station is canceled by the output of the amplitude adjustment circuit 8 and output to the AGC amplifier 12. This signal is amplified by the AGC amplifier 12, and the data signal and the clock signal are reproduced and output by the clock reproduction circuit 13 and the data reproduction circuit 14.
[0033]
Therefore, according to the optical transmission / reception apparatus of the second embodiment of the present invention, the data signal transmitted by the local station is branched into two in advance, and the phase is adjusted by the phase adjustment circuit 10, the frequency characteristic adjustment circuit 9, and the amplitude adjustment circuit 8. After adjusting the frequency characteristics and amplitude, and subtracting from the received signal, the optical crosstalk component that degrades the reception characteristics can be removed, so that the optical transmission / reception apparatus for a single-core bidirectional optical communication system having excellent reception characteristics Can be provided.
[0034]
<Third Embodiment>
FIG. 4 is a block diagram showing an optical transmission / reception apparatus according to the third embodiment of the present invention. As shown in FIG. 4, the optical transmission / reception apparatus 22 according to the third embodiment of the present invention branches the antiphase output of the buffer circuit 7 according to the first embodiment shown in FIG. Later, one is supplied to the amplitude adjustment circuit 20a via the frequency characteristic adjustment circuit 19a for adjusting the frequency characteristic and amplitude of the optical crosstalk, and the other is for adjusting the frequency characteristic and amplitude of the electrical crosstalk. The second embodiment is different from the first embodiment in that a crosstalk removing circuit 21 that supplies the amplitude adjusting circuit 20b via the frequency characteristic adjusting circuit 19b and subtracts the outputs from the preamplifier 4 by the subtracting circuits 11a and 11b is configured. .
[0035]
As shown in FIG. 3, the frequency characteristic of the frequency characteristic adjusting circuit 19a is almost equal to the sum of the frequency characteristics of the drive circuit 6, the light emitting element 1, the light receiving element 2, and the preamplifier 4, that is, the frequency characteristic of optical crosstalk. As shown in FIG. 2, the frequency characteristic adjustment circuit 19b is configured to be a capacitively coupled high-pass filter because electric crosstalk is generated by spatial coupling, that is, the frequency characteristic of electric crosstalk. It is set to be.
[0036]
The operation of the optical transceiver configured as above will be described. First, the electrical signal input to the optical transceiver 22 is branched into two by the buffer circuit 7, and one positive phase output is input to the drive circuit 6. The light emitting element 1 is driven by the drive circuit 6, so that the electric signal is converted into an optical signal, input to the transmission optical fiber 16 through the wavelength multiplexing / demultiplexing element 3, and transmitted as an optical signal. An optical signal input from the transmission optical fiber 16 is input to the light receiving element 2 through the wavelength demultiplexing element 3 and amplified by the preamplifier 4 with low noise.
[0037]
Here, the signal transmitted by the own station is also output together with the optical crosstalk represented by the solid arrow in FIG. 4 and the electrical crosstalk represented by the dotted arrow. The other antiphase output of the buffer circuit 7 is further branched into two by the branch circuit 18, and is divided into a signal for removing optical crosstalk and a signal for removing electrical crosstalk. In order to remove the optical crosstalk, the frequency characteristic adjusting circuit 19a is set to be substantially equal to the sum of the frequency characteristics of the driving circuit 6, the light emitting element 1, the light receiving element 2, and the preamplifier 4, and removes the electric crosstalk. Therefore, the frequency characteristic adjusting circuit 19b is set to be a capacitively coupled high-pass filter because electric crosstalk occurs due to spatial coupling.
[0038]
Therefore, when the subtraction circuits 11 a and 11 b subtract the output of the amplitude adjustment circuits 20 a and 21 from the output of the preamplifier 4, the crosstalk transmitted by the own station is canceled more precisely and output to the AGC amplifier 12. This signal is amplified by the AGC amplifier 12, and the data signal and the clock signal are reproduced and output by the clock reproduction circuit 13 and the data reproduction circuit 14.
[0039]
Therefore, according to the optical transmission / reception apparatus of the third embodiment of the present invention, the data signal transmitted by the own station is branched into two in advance, and the frequency characteristics and amplitude are adjusted by the frequency characteristics adjustment circuits 19a and 19b and the amplitude adjustment circuits 20a and 20b. Optical crosstalk and electrical crosstalk components that degrade reception characteristics can be removed by subtracting the received signal from the received signal after adjustment, providing an optical transceiver for single-core bidirectional optical communication systems with excellent reception characteristics can do.
[0040]
<Fourth embodiment>
FIG. 5 is a block diagram showing an optical transmission system according to the fourth embodiment of the present invention. The optical transmission / reception devices 23 and 24 have the same configuration as that of the optical transmission / reception devices shown in the first to third embodiments, so that communication can be established with each other, that is, the optical transmission / reception devices. The optical transmission / reception device 24 can receive the wavelength of the optical signal output by the optical transmission / reception device 23, and the optical transmission / reception device 23 sets the wavelength of the optical signal output by the optical transmission / reception device 24 (a wavelength different from the wavelength of the optical signal output by the optical transmission / reception device 23). The light emitting element, the light receiving element, and the wavelength demultiplexing element are selected so that can be received. The optical transceivers 23 and 24 are connected to each other by the transmission optical fiber 16 and are opposed to each other.
[0041]
The operation of the optical transmission system configured as described above will be described. When the data signal (DATA) is input to the optical transmitter / receiver 23, it is converted into an optical signal and input to the transmission optical fiber 16. Thereafter, the data is transmitted through the transmission optical fiber 16 and input to the optical transmission / reception device 24 to output a data signal and a clock signal (CLK). Similarly, when a data signal is input to the optical transmitter / receiver 24, it is converted into an optical signal and input to the transmission optical fiber 16. Thereafter, the signal is transmitted through the transmission optical fiber 16 and input to the optical transmitter / receiver 23 to output a data signal and a clock signal.
[0042]
Thus, according to the optical transmission system of the fourth embodiment of the present invention, it is possible to realize good single-core bidirectional optical transmission without the optical signal of the local station interfering with the received optical signal. Can do.
[0043]
【The invention's effect】
As described above, according to the present invention, an input electrical data signal is branched into two, one branched electrical data signal is converted into an optical signal and transmitted, and the other branched electrical data signal is transmitted. Frequency is adjusted by a frequency characteristic adjustment circuit that has a frequency characteristic almost equal to the frequency characteristic of electrical crosstalk, and transmission is performed by subtracting the frequency-adjusted electrical signal from the electrical signal converted from the optical signal received via the optical fiber. A crosstalk removing method, a crosstalk removing circuit, and a crosstalk removing circuit capable of removing an electrical crosstalk or an optical cross stroke that leaks into a received signal and obtaining an excellent reception characteristic by removing the crosstalk signal. An optical transmission / reception apparatus and an optical transmission / reception system provided with
[Brief description of the drawings]
FIG. 1 is a block diagram showing an optical transceiver according to a first embodiment of the present invention. FIG. 2 is a frequency characteristic diagram of a frequency characteristic adjusting circuit according to the first embodiment of the present invention. FIG. 4 is a frequency characteristic diagram of a frequency characteristic adjusting circuit according to a second embodiment of the present invention. FIG. 4 is a block diagram showing an optical transceiver according to a third embodiment of the present invention. FIG. 6 is a block diagram showing a conventional optical transmission / reception apparatus. FIG. 7 is a frequency characteristic diagram of optical crosstalk. FIG. 8 is a frequency characteristic diagram of electrical crosstalk. Explanation】
DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Light receiving element 3 Wavelength demultiplexing element 4 Preamplifier 5 Optical module 6 Drive circuit 7 Buffer circuit 8, 20a, 20b Amplitude adjustment circuit 9, 19a, 19b Frequency characteristic adjustment circuit 10 Phase adjustment circuit 11, 11a, 11b Subtraction circuit 12 AGC amplifier 13 Clock recovery circuit 14 Data recovery circuit 15, 22, 23, 24 Optical transceiver 16 Transmission optical fiber 17, 21 Crosstalk removal circuit 18 Branch circuit

Claims (11)

Branch the input electrical data signal into two,
One of the branched electrical data signals is converted into an optical signal and transmitted.
The frequency of the other branched electric data signal is adjusted by a frequency characteristic adjustment circuit having a frequency characteristic substantially equal to the frequency characteristic of electric crosstalk,
A crosstalk elimination method for removing electrical crosstalk in which a transmission signal leaks into a reception signal by subtracting the frequency-adjusted electrical signal from an electrical signal obtained by converting an optical signal received via an optical fiber. Branch the input electrical data signal into two,
One of the branched electrical data signals is converted into an optical signal and transmitted.
The frequency of the other branched electrical data signal is adjusted by a frequency characteristic adjustment circuit having a frequency characteristic substantially equal to the frequency characteristic of optical crosstalk,
A crosstalk removal method for removing optical crosstalk in which a transmission signal leaks into a reception signal by subtracting the frequency-adjusted electric signal from an electric signal obtained by converting an optical signal received via an optical fiber. A branch circuit for branching the input electrical data signal;
A frequency characteristic adjusting circuit for adjusting a frequency characteristic of one output signal of the branch circuit;
A cross comprising: an amplitude adjusting circuit for adjusting an amplitude level of an output signal of the frequency characteristic adjusting circuit; and a subtracting circuit for subtracting the output signal of the amplitude adjusting circuit from an electric signal obtained by converting an optical signal input from an optical fiber. Talk elimination circuit. The crosstalk elimination circuit according to claim 3, wherein the frequency characteristic adjusting circuit has a frequency characteristic substantially equal to a frequency characteristic of electrical crosstalk. 4. The crosstalk elimination circuit according to claim 3, wherein the frequency characteristic adjustment circuit has a frequency characteristic substantially equal to a frequency characteristic of an optical cross stroke. The branch circuit is a buffer circuit that inputs an electrical signal and sends out a positive phase output and a negative phase output,
The frequency characteristic adjustment circuit is a high-pass filter that passes a high-frequency component of the anti-phase output of the buffer circuit,
The crosstalk elimination circuit according to claim 4, wherein the amplitude adjustment circuit is a resistance element. The branch circuit is a buffer circuit that inputs an electrical signal and sends out a positive phase output and a negative phase output,
The frequency characteristic adjustment circuit is a low-pass filter that passes a low-frequency component of the anti-phase output of the buffer circuit,
The crosstalk elimination circuit according to claim 5, wherein the amplitude adjustment circuit is a resistance element. The crosstalk elimination circuit according to any one of claims 3 to 7, further comprising a phase adjustment circuit that adjusts a phase of a signal whose frequency characteristics are adjusted. The crosstalk elimination circuit according to any one of claims 4, 6, and 8, and the crosstalk elimination circuit according to any one of claims 5, 7, and 8,
Provided crosstalk elimination circuit. A crosstalk elimination circuit according to any one of claims 3 to 9,
An optical transmitter having a drive circuit that inputs the other output signal of the branch circuit, and a light emitting element that drives based on the output of the drive circuit and outputs an optical signal;
An optical receiver having a light receiving element that receives an optical signal output from the light emitting element and an optical signal input from a transmission optical fiber and converts the received optical signal into an electrical signal; and a preamplifier that amplifies the output of the light receiving element;
An amplification circuit that amplifies a signal obtained by subtracting the output of the amplitude adjustment circuit from the output of the optical receiver by the subtraction circuit;
An optical transmission / reception apparatus comprising: an electric circuit that regenerates a data signal and a clock signal from an output signal of the amplification circuit. The optical transmission / reception apparatus according to claim 10, comprising two optical transmission / reception apparatuses having different wavelengths of an optical signal to be transmitted and an optical signal to be received, wherein the two optical transmission / reception apparatuses are connected by an optical fiber to face each other. system.

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