Optical transmitter / receiver

Abstract

The present invention is provided with: a pseudo-random number code generator (101) that outputs a signal indicating a pseudo-random number code; a digital optical transmitter (102) that generates and transmits transmission light on the basis of the signal indicating a pseudo-random number code, and supports 1 Gb / s or higher transmission; an analog optical receiver (104) that receives input light as reception light and converts the reception light into a reception signal; a transmission / reception switch that outputs the transmission light to one end of the optical fiber (2), and outputs light from the optical fiber (2) to the analog optical receiver (104); an ADC (105) that converts the reception signal into a digital signal; a correlation processing unit (106) that calculates loss curve data by performing correlation processing between the signal indicating a pseudo random number code and the reception signal obtained by the ADC (105); a differential processing unit (107) that calculates loss curve differential data by performing differential processing on the basis of the loss curve data; and a difference calculation unit (109) that calculates a difference between the loss curve differential data and loss differential data before the optical fiber (2) is installed.

Description

Optical Transceiver

[0001] The present disclosure relates to an optical transceiver capable of measuring optical loss.

[0002] Conventionally, devices for obtaining radiation dose distribution information are known (see, for example, Patent Document 1). The device disclosed in Patent Document 1 uses a single-pulse OTDR measurement method driven by a light source with a pulse width tw and a pulse period tp to obtain radiation dose distribution information along a sensor optical fiber. This method estimates the radiation exposure dose by processing multiple wavelengths, such as Stokes light and anti-Stokes light, using the wavelength dependency (difference) of the amount of degradation due to radiation. Patent Document 1 also states that a pseudo-random pulse OTDR measurement method driven by a pulse train may also be used.

[0003] Japanese Patent Application Publication No. 04-274787

[0004] However, with the conventional method disclosed in Patent Document 1, it is difficult to measure radiation dose distribution with high distance resolution. Furthermore, it is difficult to measure not only radiation dose distribution but also optical loss with high distance resolution. Furthermore, with the conventional method, when the OTDR transmission light is pulse-narrowed to achieve high resolution, the backscattering power decreases. Therefore, in this case, the dynamic range of the measurement distance decreases, and the loss of the optical fiber increases in a radiation environment, making it difficult to maintain the measurement range.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an optical transceiver that can measure optical loss with higher distance resolution than conventional ones.

[0006] The optical transceiver according to the present disclosure includes a pseudorandom code generator that outputs a signal indicative of a pseudorandom code; a digital optical transmitter capable of transmitting at 1 Gbit or more that generates and transmits transmission light based on the signal indicative of the pseudorandom code output by the pseudorandom code generator; an analog optical receiver that receives input light as reception light and converts the reception light into a reception signal; a transmission / reception switch that outputs the transmission light transmitted by the digital optical transmitter to one end of an optical fiber and outputs the light from the optical fiber to an analog optical receiver; and an analog-to-digital converter that converts the reception signal obtained by the analog optical receiver from an analog signal to a digital signal. a correlation processing unit that calculates loss curve data by performing correlation processing between the signal indicating the pseudorandom number code output by the pseudorandom number code generator and the received signal obtained by the analog-to-digital converter, a differentiation processing unit that calculates loss curve differential data by performing differentiation processing based on the loss curve data calculated by the correlation processing unit, and a difference calculation unit that calculates a difference between the loss curve differential data and the loss curve differential data based on the loss differential data before the optical fiber is installed and the loss curve differential data calculated by the differentiation processing unit.

[0007] According to the present disclosure, the above-described configuration makes it possible to measure optical loss with higher distance resolution than conventionally possible.

[0008] 1 is a block diagram showing an example of a configuration of an optical transceiver according to a first embodiment. FIG. 2 is a flowchart showing an example of operation of the optical transceiver according to the first embodiment. FIG. 3 is a diagram showing an example of loss data and loss curve data handled by the optical transceiver according to the first embodiment. FIG. 4 is a diagram showing an example of loss differential data, loss curve differential data, and cumulative absorption line distribution handled by the optical transceiver according to the first embodiment. FIG. 5 is a block diagram showing an example of a configuration of an optical transceiver according to a second embodiment. FIG. 6 is a block diagram showing an example of a configuration of a receiving side of a digital optical transceiver according to the second embodiment. FIG. 7 is a diagram for explaining the gain of an LA in the optical transceiver according to the second embodiment (when leaky light is used). FIG. 8 is a diagram for explaining the gain of an LA in the optical transceiver according to the second embodiment (when leaky light is small or when leaky light is not used). FIG. 9 is a block diagram showing an example of a configuration of an optical transceiver system according to a third embodiment. FIG. 10 is a block diagram showing another example of a configuration of an optical transceiver system according to the third embodiment. FIG. 11 is a block diagram showing an example of a configuration of an optical transceiver system according to a fourth embodiment. FIG. 12 is a flowchart showing an example of operation of the optical transceiver system according to the fourth embodiment. FIG. 13 is a diagram showing an example of loss data and loss curve data handled by a first optical transceiver and a second optical transceiver according to the fourth embodiment. 16A and 16B are block diagrams showing examples of the hardware configuration of the optical transceivers according to the first to fourth embodiments.

[0009] Hereinafter, embodiments will be described in detail with reference to the drawings. Embodiment 1. FIG. 1 is a diagram showing an example of the configuration of an optical transceiver 1 according to embodiment 1. FIG. 1 shows an example in which the optical transceiver 1 is a fiber-type radiation distribution meter that measures an accumulated absorption dose distribution (radiation dose distribution). Note that FIG. 1 also shows an example in which an optical fiber 2 is attached to an object to be measured that is irradiated with radiation via an adhesive. In FIG. 1, multiple arrows shown above the optical fiber 2 indicate the irradiation of radiation. Note that this optical transceiver 1 can be applied, for example, to satellites and power plants such as nuclear reactors. For example, even if the optical transceiver 1 is applied in a place where people cannot enter, such as a nuclear reactor, the optical transceiver 1 can remotely measure the accumulated absorption dose distribution.

[0010] 1, the optical transceiver 1 includes a pseudorandom code generator 101, a digital optical transmitter 102, an optical circulator (transmitter / receiver switch) 103, an analog optical receiver 104, an ADC (analog-to-digital converter) 105, a correlation processing unit 106, a differential processing unit 107, a differential data acquisition unit 108, and a difference calculation unit 109. The optical transceiver 1 is provided on one end side of an optical fiber 2.

[0011] The pseudorandom code generator 101 generates a pseudorandom code. That is, the pseudorandom code generator 101 generates a code in which "0" or "1" is randomly arranged. A signal indicating the pseudorandom code generated by the pseudorandom code generator 101 is output to the digital optical transmitter 102 and the correlation processing unit 106.

[0012] The digital optical transmitter 102 generates transmission light based on a signal indicating the pseudorandom code output by the pseudorandom code generator 101, and transmits the generated light to the optical circulator 103. The transmission light generated by the digital optical transmitter 102 is continuous light. The digital optical transmitter 102 is a digital optical transmitter capable of transmitting at 1 Gbit or more.

[0013] For example, an SFP (Small Form-factor Pluggable) can be used as this digital optical transmitter 102. Furthermore, the digital optical transmitter 102 is not limited to an SFP, and a higher speed transmitter such as an SFP+, QSFP, or SFP28 can also be used as long as it is a digital optical transmitter that performs OOK (On-Off-Keying) digital modulation.

[0014] The optical circulator 103 outputs the transmission light transmitted by the digital optical transmitter 102 to one end of the optical fiber 2. The optical circulator 103 also outputs the light (backscattered light) from the optical fiber 2 to the analog optical receiver 104.

[0015] 1 shows a case where an optical circulator 103 is used as a transmission / reception switch, but the transmission / reception switch is not limited to this, and for example, an optical coupler may be used as a transmission / reception switch.

[0016] The analog optical receiver 104 receives the light from the optical circulator 103 as received light and converts the received light into a received signal. The received signal obtained by the analog optical receiver 104 is an analog signal. The received signal obtained by the analog optical receiver 104 is output to the ADC 105.

[0017] The analog optical receiver 104 may be, for example, a photodiode (PD).

[0018] The ADC 105 converts the received signal obtained by the analog optical receiver 104 from an analog signal to a digital signal based on the received signal. The digital received signal obtained by the ADC 105 is output to the correlation processing unit 106.

[0019] In order to improve the SNR of the received signal, the ADC 105 may obtain the received signal to be output to the correlation processing unit 106 by acquiring the received signal multiple times and performing averaging processing on the multiple received signals.

[0020] The correlation processing unit 106 calculates loss curve data by performing correlation processing between the signal indicating the pseudorandom code output by the pseudorandom code generator 101 and the received signal obtained by the ADC 105. This loss curve data is data indicating optical loss in the distance direction along the optical fiber 2. A conventionally known calculation method can be applied to the calculation of the loss curve data by the correlation processing unit 106, and a description thereof will be omitted. The loss curve data calculated by the correlation processing unit 106 is output to the differentiation processing unit 107.

[0021] The differential processing unit 107 calculates loss curve differential data by performing differential processing based on the loss curve data calculated by the correlation processing unit 106. This loss curve differential data is data that indicates the rate of change of optical loss in the distance direction along the optical fiber 2. The loss curve differential data calculated by the differential processing unit 107 is output to the difference calculation unit 109.

[0022] The differential data acquiring unit 108 acquires loss differential data before the installation of the optical fiber 2. The loss differential data is data that indicates the rate of change of optical loss in the distance direction along the optical fiber 2 in a state before the optical fiber 2 is placed in a radiation environment, and is measured in advance. The loss differential data acquired by the differential data acquiring unit 108 is output to the difference calculating unit 109.

[0023] The difference calculation unit 109 calculates the difference between the loss differential data acquired by the differential data acquisition unit 108 and the loss curve differential data calculated by the differential processing unit 107. This difference indicates the optical loss per unit length in the distance direction along the optical fiber 2. Furthermore, when the optical transceiver 1 functions as a fiber-type radiation distribution meter, the difference calculation unit 109 calculates an accumulated absorbed ray dose distribution based on the calculated difference. This accumulated absorbed ray dose distribution is a distribution that indicates the radiation dose in the distance direction along the optical fiber 2.

[0024] Next, an example of operation of the optical transceiver 1 according to the first embodiment shown in Fig. 1 will be described with reference to Fig. 2. That is, the following describes an example of operation in the case where the optical transceiver 1 functions as a fiber-type radiation distribution meter. In the example of operation of the optical transceiver 1 according to the first embodiment shown in Fig. 1, as shown in Fig. 2, for example, first, the pseudo-random code generator 101 generates a pseudo-random code (step ST101). A signal indicating the pseudo-random code generated by the pseudo-random code generator 101 is output to the digital optical transmitter 102 and the correlation processing unit 106.

[0025] Next, the digital optical transmitter 102 generates transmission light based on a signal indicating the pseudorandom code output by the pseudorandom code generator 101 and transmits it to the optical circulator 103, and the optical circulator 103 outputs the transmission light to one end of the optical fiber 2 (step ST102).

[0026] Next, the optical circulator 103 outputs the light (backscattered light) from the optical fiber 2 to the analog optical receiver 104, which receives the light as received light and converts the received light into a received signal (step ST103). The received signal obtained by the analog optical receiver 104 is output to the ADC 105.

[0027] Next, the ADC 105 converts the received signal obtained by the analog optical receiver 104 from an analog signal to a digital signal (step ST104). The received signal, which is a digital signal obtained by the ADC 105, is output to the correlation processing unit 106.

[0028] Next, the correlation processing unit 106 calculates loss curve data by performing correlation processing between the signal representing the pseudorandom code output by the pseudorandom code generator 101 and the received signal obtained by the ADC 105 (step ST105), based on the signal representing the pseudorandom code and the received signal. The loss curve data calculated by the correlation processing unit 106 is output to the differentiation processing unit 107.

[0029] Next, the differential processing unit 107 calculates loss curve differential data by performing differential processing based on the loss curve data calculated by the correlation processing unit 106 (step ST106). The loss curve differential data calculated by the differential processing unit 107 is output to the difference calculation unit 109.

[0030] The differential data acquiring unit 108 also acquires loss differential data before the installation of the optical fiber 2 (step ST107). The loss differential data acquired by the differential data acquiring unit 108 is output to the difference calculating unit 109.

[0031] Next, based on the loss differential data acquired by the differential data acquisition unit 108 and the loss curve differential data calculated by the differential processing unit 107, the difference calculation unit 109 calculates the difference between the loss differential data and the loss curve differential data, thereby calculating the cumulative absorption line amount distribution (step ST108).

[0032] FIG. 3 shows an example of loss data and loss curve data handled by the optical transceiver 1 according to the first embodiment. In FIG. 3, reference numeral 31 denotes loss data (Lo(x)) before the installation of the optical fiber 2, reference numeral 32 denotes loss curve data (L(x)), and reference numeral 33 denotes loss curve data (L(x)) in the case where the optical devices (the digital optical transmitter 102 and the analog optical receiver 104) have deteriorated. In the example shown in FIG. 3, reference numeral 34 denotes a location where the optical power has significantly decreased and is a location that has been heavily exposed to radiation. As shown in FIG. 3, in the loss curve data in the case where the optical device has deteriorated, reference numeral 33, the optical power decreases overall due to the deterioration of the optical device, compared to the loss curve data in the case where the optical device has not deteriorated, reference numeral 32.

[0033] FIG. 4 shows an example of the loss differential data, loss curve differential data, and cumulative absorption ray distribution handled by the optical transceiver 1 according to the first embodiment. In FIG. 4, reference numeral 41 denotes the loss differential data ({Lo(x)}') before the installation of the optical fiber 2, reference numeral 42 denotes the loss curve differential data ({L(x)}'), and reference numeral 43 denotes the loss curve differential data ({L(x)}') when the optical device has deteriorated. In the example shown in FIG. 4, the location indicated by reference numeral 44 is a location where power is significantly reduced and is a location that has been heavily exposed to radiation. As shown in FIG. 4, the cumulative absorption ray distribution is E(x) = S{Lo(x) - L(x)}'. S is a coefficient ([Gy / (dB / m)]) that indicates the relationship between the amount of deterioration of the sensor optical fiber 2 and the radiation dose, and is measured in advance. As shown in FIG. 4, the loss curve differential data in the case where the optical device is degraded, indicated by the reference numeral 43, does not change from the loss curve differential data in the case where the optical device is not degraded, indicated by the reference numeral 42, regardless of the degradation of the optical device.

[0034] In this way, in the optical transceiver 1 according to the first embodiment, it is possible to measure the optical loss and the radiation dose distribution without being affected by the deterioration of the optical device due to radiation irradiation by taking the difference between the loss differential data and the loss curve differential data before the installation of the optical fiber 2. That is, in the optical transceiver 1 according to the first embodiment, by taking the difference between the loss differential data and the loss curve differential data before the installation of the optical fiber 2, the measurement results of the optical loss and the measurement results of the radiation dose do not change depending on whether the optical device has deteriorated.

[0035] Furthermore, in the prior art, the resolution was limited by the size of the optical fiber 2 and the pulse width of the transmitted light. In contrast, the optical transceiver 1 according to the first embodiment can obtain high-resolution data corresponding to the bit rate of the digital optical transmitter 102. Therefore, the optical transceiver 1 according to the first embodiment can detect a local increase in the amount of radiation exposure by differential processing.

[0036] As described above, according to the first embodiment, the optical transceiver 1 comprises a pseudo-random code generator 101 that outputs a signal indicative of a pseudo-random code, a digital optical transmitter 102 that generates and transmits transmission light based on the signal indicative of the pseudo-random code output by the pseudo-random code generator 101 and is capable of transmitting at 1 Gbit or more, an analog optical receiver 104 that receives input light as reception light and converts the reception light into a reception signal, a transmission / reception switch that outputs the transmission light transmitted by the digital optical transmitter 102 to one end of the optical fiber 2 and outputs the light from the optical fiber 2 to the analog optical receiver 104, and a signal receiving switch that converts the reception signal into an analog signal based on the reception signal obtained by the analog optical receiver 104. The optical transceiver 1 according to the first embodiment includes an ADC 105 that converts a signal from a pseudorandom code generator 101 into a digital signal, a correlation processor 106 that calculates loss curve data by performing correlation processing between the signal indicating the pseudorandom code and the received signal based on the signal indicating the pseudorandom code output by the pseudorandom code generator 101 and the received signal obtained by the ADC 105, a differential processor 107 that calculates loss curve differential data by performing differential processing based on the loss curve data calculated by the correlation processor 106, and a difference calculator 109 that calculates a difference between the loss curve differential data and the loss curve differential data based on the loss differential data before the installation of the optical fiber 2 and the loss curve differential data calculated by the differential processor 107. Furthermore, according to the first embodiment, the digital optical transmitter 102 is a digital optical transmitter that performs OOK modulation. These features enable the optical transceiver 1 according to the first embodiment to measure optical loss with higher distance resolution than conventional devices.

[0037] According to the first embodiment, the difference calculation unit 109 may calculate the cumulative absorbed radiation dose distribution based on the calculated difference, thereby enabling the optical transceiver 1 according to the first embodiment to measure the radiation dose distribution with higher distance resolution than conventional methods.

[0038] Second Embodiment Fig. 5 is a diagram showing a configuration example of an optical transceiver 1 according to a second embodiment. In the optical transceiver 1 according to the second embodiment shown in Fig. 5, the digital optical transmitter 102 and the analog optical receiver 104 are configured as a digital optical transceiver 110, in contrast to the optical transceiver 1 according to the first embodiment shown in Fig. 1. The other configuration example of the optical transceiver 1 according to the second embodiment shown in Fig. 5 is the same as the configuration example of the optical transceiver 1 according to the first embodiment, and the same reference numerals are used, and only the different parts will be described.

[0039] The transmitting side of the digital optical transceiver 110 generates transmission light based on a signal indicating the pseudorandom code output by the pseudorandom code generator 101 and outputs the generated light to the optical circulator 103. The receiving side of the digital optical transceiver 110 receives light (backscattered light and leaked light) from the optical circulator 103 as received light and converts the received light into a received signal. The received signal obtained by the receiving side of the digital optical transceiver 110 is output to the ADC 105. The receiving side of the digital optical transceiver 110 fixes the gain of the LA 1043 (described later) using the leaked light from the optical circulator 103. This digital optical transceiver 110 is capable of transmitting at 1 Gbit or more.

[0040] For example, an SFP transmission port and a reception port can be used as this digital optical transceiver 110. Furthermore, the digital optical transceiver 110 is not limited to an SFP, and higher speed transceivers such as SFP+, QSFP, and SFP28 can also be used as long as they are digital optical transceivers that perform OOK digital modulation. For example, a PAM4 (4 Pulse Amplitude Modulation) digital optical transceiver can be used as this digital optical transceiver 110.

[0041] The optical circulator 103 outputs, to the receiving side of the digital optical transceiver 110, leakage light that is a leakage light of the transmitted light transmitted by the transmitting side of the digital optical transceiver 110 and that is capable of fixing the gain of the LA 1043. The leakage light is, for example, −20 dB or more.

[0042] Also, as shown in FIG. 6, for example, the receiving side of the digital optical transceiver 110 generally comprises a PD 1041, a TIA (transimpedance amplifier) ​​1042, and an LA (limiting amplifier) ​​1043.

[0043] The PD 1041 receives light from the optical circulator 103 as received light and converts the received light into an electrical signal. The electrical signal obtained by the PD 1041 is output to the TIA 1042. The TIA 1042 converts the current of the electrical signal into a voltage based on the electrical signal converted by the PD 1041. The electrical signal converted by the TIA 1042 is output to the LA 1043. The LA 1043 performs limiting on the electrical signal based on the electrical signal converted by the TIA 1042. The electrical signal processed by the LA 1043 is output to the ADC 105 as a received signal.

[0044] Here, the LA 1043 operates such that the gain increases or decreases according to the average optical power and saturates the voltage amplitude of the input electrical signal with that gain. In contrast, leakage light is transmitted light modulated with a pseudorandom code that has suffered a certain loss, and its average power does not fluctuate over time. Therefore, by inputting this leakage light into the LA 1043, the gain of the LA 1043 is determined according to the average power of the leakage light. As a result, Rayleigh scattering components that are less than the leakage light and do not contribute significantly to the average power are output with approximately a constant gain regardless of the detection time. Note that the detection time is proportional to the distance.

[0045] For example, on the left side of FIG. 7 , reference numeral 71 denotes the output power of the leaked light component from the TIA 1042, reference numeral 72 denotes the output power of the Rayleigh scattering component from the TIA 1042 when the detection time is t1, and reference numeral 73 denotes the output power of the Rayleigh scattering component from the TIA 1042 when the detection time is t2 (≠t1). Reference numeral 74 denotes the output power of the leaked light component from the LA 1043, which outputs leaked light of a constant power. Reference numeral 75 denotes the output power of the Rayleigh scattering component from the LA 1043 when the detection time is t1, and reference numeral 76 denotes the output power of the Rayleigh scattering component from the LA 1043 when the detection time is t2. As shown on the left side of FIG. 7 , the leaked light constantly input to the receiving side of the digital optical transceiver 110 has a higher input power than the Rayleigh scattering component. Therefore, the gain (G) of the LA 1043 is fixed to a gain that saturates this leaked light. As a result, the Rayleigh scattering component when the detection time is t1 and the Rayleigh scattering component when the detection time is t2 are output with a common gain (G) regardless of the difference in detection time, and become analog values.

[0046] On the other hand, as shown on the right side of Figure 7, in the correlation processing, the leakage light component has a high correlation gain only at the point corresponding to the most recent time (near t = 0, as indicated by reference numeral 77). Therefore, for times when the correlation value between the leakage light component and the pseudorandom number code is low, the Rayleigh scattering component can be detected, and accurate loss curve data can be obtained. Note that on the right side of Figure 7, reference numeral 78 indicates the noise level due to leakage light.

[0047] In this way, more accurate loss curve data can be obtained by fixing the gain of the LA 1043 based on the leakage light component. In contrast, in the optical transceiver 1 according to the second embodiment, when the leakage light component is small or absent, the expected operation cannot be achieved.

[0048] That is, as shown on the left side of Fig. 8, when the leakage light component is small or absent, in the LA1043, when the detection time is t1, the gain (G1) is fixed to a gain that saturates the Rayleigh scattering component when the detection time is t1, and when the detection time is t2, the gain (G2) is fixed to a gain that saturates the Rayleigh scattering component when the detection time is t2. In this case, as shown on the right side of Fig. 8, the output power of the Rayleigh scattering component when the detection time is t1 and the Rayleigh scattering component when the detection time is t2 are approximately the same, resulting in no loss change and an incorrect loss curve. In Fig. 8, reference numeral 81 denotes the output power of the Rayleigh scattering component from the LA1043 when the detection times are t1 and t2.

[0049] Other operational examples of the optical transceiver 1 according to the second embodiment are the same as those of the optical transceiver 1 according to the first embodiment.

[0050] As described above, according to the second embodiment, the digital optical transmitter 102 and the analog optical receiver 104 are configured using the digital optical transceiver 110, the receiving side of the digital optical transceiver 110 has the LA 1043, and the duplexer outputs, to the receiving side of the digital optical transceiver 110, leakage light of the transmitted light transmitted by the transmitting side of the digital optical transceiver 110, which leakage light is capable of fixing the gain of the LA 1043. Furthermore, according to the second embodiment, the leakage light is −20 dB or more. As a result, in addition to the effects of the optical transceiver 1 according to the first embodiment, the optical transceiver 1 according to the second embodiment can use inexpensive digital optical transceivers 110 as the digital optical transmitter 102 and the analog optical receiver 104, thereby enabling the optical transceiver 1 to be configured inexpensively.

[0051] Embodiment 3. In the second embodiment, the case where the leaked light is used to fix the gain of the LA 1043 is shown. In contrast to this, the third embodiment shows the case where the gain of the LA 1043 is fixed by using the transmitted light (dummy light) transmitted from the opposing optical transceiver 1.

[0052] 9 is a diagram showing an example of the configuration of an optical transceiver system according to a third embodiment. The optical transceiver system includes a pair of optical transceivers 1 (a first optical transceiver 1-1 and a second optical transceiver 1-2). The first optical transceiver 1-1 and the second optical transceiver 1-2 have the same configuration. The first optical transceiver 1-1 and the second optical transceiver 1-2 are arranged opposite each other via an optical fiber 2. That is, the first optical transceiver 1-1 is provided at one end of the optical fiber 2, and the second optical transceiver 1-2 is provided at the other end of the optical fiber 2. Note that the detailed configuration of the second optical transceiver 1-2 is omitted from FIG. 9.

[0053] In the optical transceiver 1 provided in the optical transmission and reception system according to the third embodiment shown in Fig. 9, the digital optical transmitter 102 and analog optical receiver 104 are configured using a digital optical transceiver 110, and a dummy code generator 111, a selector 112, and an optical power adjustment unit 113 are added to the optical transceiver 1 according to the first embodiment shown in Fig. 1. Other configuration examples of the optical transceiver 1 provided in the optical transmission and reception system according to the third embodiment shown in Fig. 9 are similar to the configuration example of the optical transceiver 1 according to the first embodiment shown in Fig. 1, and the same reference numerals are used and only the different parts will be described.

[0054] The dummy code generator 111 generates a dummy code. The dummy code is a code that has no correlation with the pseudo-random code used in the opposing optical transceiver 1. A signal indicating the dummy code generated by the dummy code generator 111 is output to the selector 112.

[0055] The selector 112 outputs a signal indicating the pseudorandom code output by the pseudorandom code generator 101 or a signal indicating the dummy code output by the dummy code generator 111 to the transmitting side of the digital optical transceiver 110.

[0056] Here, when the selector 112 performs measurement itself, it outputs a signal indicating the pseudo-random code output by the pseudo-random code generator 101 to the transmission side of the digital optical transceiver 110. That is, in this case, the selector 112 does not output a signal indicating the dummy code output by the dummy code generator 111 to the transmission side of the digital optical transceiver 110. On the other hand, when the opposing optical transceiver 1 performs measurement, the selector 112 outputs a signal indicating the dummy code output by the dummy code generator 111 to the transmission side of the digital optical transceiver 110. That is, in this case, the selector 112 does not output a signal indicating the pseudo-random code output by the pseudo-random code generator 101 to the transmission side of the digital optical transceiver 110.

[0057] The transmitting side of the digital optical transceiver 110 generates transmission light based on the signal output by the selector 112 and outputs it to the optical circulator 103. When the digital optical transceiver 110 generates transmission light modulated with the dummy code output by the dummy code generator 111, this transmission light is also referred to as dummy light. If the dummy code is a code consisting entirely of "1", the dummy light becomes CW light. The receiving side of the digital optical transceiver 110 receives the light (backscattered light and dummy light) from the optical circulator 103 as received light and converts the received light into a received signal. The received signal obtained by the receiving side of the digital optical transceiver 110 is output to the ADC 105. The receiving side of the digital optical transceiver 110 fixes the gain of the LA 1043 using the dummy light from the optical circulator 103. This digital optical transceiver 110 is capable of transmitting at 1 Gbit or more.

[0058] For example, an SFP transmission port and a reception port can be used as this digital optical transceiver 110. Furthermore, the digital optical transceiver 110 is not limited to an SFP, and higher-speed transceivers such as SFP+, QSFP, and SFP28 can also be used, as long as they are digital optical transceivers that perform OOK digital modulation. For example, a PAM4 digital optical transceiver can be used as this digital optical transceiver 110.

[0059] The configuration of this digital optical transceiver 110 itself is similar to that of the digital optical transceiver 110 shown in the second embodiment.

[0060] The optical power adjuster 113 adjusts the optical power of the transmitted light on the transmitting side of the digital optical transceiver 110. Note that the optical power adjuster 113 is not an essential component of the optical transceiver 1, and does not necessarily have to be provided in the optical transceiver 1.

[0061] 9 shows a case where a dummy code generator 111 that generates a dummy code is provided in the optical transceiver 1, separate from the pseudo-random code generator 101. However, this is not limiting, and for example, as shown in Fig. 10, the dummy code generator 111 may not be provided in the optical transceiver 1, and the pseudo-random code generator 101 may generate a dummy code that is uncorrelated with the pseudo-random code in the opposing optical transceiver 1, in addition to the pseudo-random code. In this case, as shown in Fig. 10, the selector 112 is not necessary in the optical transceiver 1.

[0062] 10 , when the pseudo-random code generator 101 performs measurement itself, it generates a pseudo-random code and outputs a signal indicating the pseudo-random code to the transmission side of the digital optical transceiver 110. That is, in this case, the pseudo-random code generator 101 does not generate a dummy code. On the other hand, when the opposing optical transceiver 1 performs measurement, the pseudo-random code generator 101 generates a dummy code and outputs a signal indicating the dummy code to the transmission side of the digital optical transceiver 110. That is, in this case, the pseudo-random code generator 101 does not generate a pseudo-random code.

[0063] Next, an example of the operation of the optical transmission and reception system according to the third embodiment will be described. Here, a case where the first optical transceiver 1-1 performs measurement will be described. When the first optical transceiver 1-1 performs measurement, the second optical transceiver 1-2 transmits dummy light toward the first optical transceiver 1-1 via the optical fiber 2. The dummy code that forms the basis of this dummy light is a dummy code that is uncorrelated with the pseudo-random code used by the first optical transceiver 1-1. The first optical transceiver 1-1 then fixes the gain of the LA 1043 on the receiving side of its own digital optical transceiver 110 using this dummy light from the second optical transceiver 1-2. That is, in the optical transmission and reception system according to the third embodiment, the gain of the LA 1043 is fixed using dummy light, rather than using leakage light as described in the second embodiment.

[0064] If the level of the dummy light is too high, the noise floor will be too high after the correlation process, making it impossible to measure. In such a case, the optical power adjuster 113 adjusts the optical power of the digital optical transceiver 110 to a measurable level by lowering it.

[0065] Other operational examples of the optical transceiver 1 according to the third embodiment are the same as those of the optical transceiver 1 according to the first embodiment.

[0066] As described above, according to the third embodiment, the digital optical transmitter 102 and the analog optical receiver 104 are configured by the digital optical transceiver 110, the receiving side of which includes the LA 1043, and the transmit / receive switch outputs, to the receiving side of the digital optical transceiver 110, transmitted light input via the optical fiber 2 from the optical transceiver 1 provided at the other end of the optical fiber 2 and based on a dummy code uncorrelated with the pseudo-random code used by the optical transceiver 1 itself. Also, according to the third embodiment, the digital optical transceiver 110 includes a dummy code generator 111 that outputs a signal indicating a dummy code uncorrelated with the pseudo-random code used by the optical transceiver 1 provided at the other end of the optical fiber 2, and a selector 112 that outputs a signal indicating the pseudo-random code output by the pseudo-random code generator 101 or a signal indicating the dummy code output by the dummy code generator 111, and the transmitting side of the digital optical transceiver 110 generates and outputs transmitted light based on the signal output by the selector 112. Alternatively, according to the third embodiment, the pseudo-random code generator 101 outputs a signal indicating a pseudo-random code or a signal indicating a dummy code that is uncorrelated with the pseudo-random code used in the optical transceiver 1 provided at the other end of the optical fiber 2, and the transmitting side of the digital optical transceiver 110 generates and outputs transmission light based on the signal output by the pseudo-random code generator 101. As a result, the optical transceiver 1 according to the third embodiment not only achieves the effects of the optical transceiver 1 according to the first embodiment, but also enables the use of inexpensive digital optical transceivers 110 as the digital optical transmitter 102 and the analog optical receiver 104, thereby enabling the optical transceiver 1 to be configured at low cost. Furthermore, the optical transmission and reception system according to the third embodiment can relax specification requirements, such as the leakage light level in the transmit / receive switch, compared to the optical transceiver 1 according to the second embodiment, thereby enabling the level adjustment performance of the optical transceiver 1 to be improved.

[0067] Fourth Embodiment Fig. 11 is a diagram showing a configuration example of an optical transmission and reception system according to a fourth embodiment. The optical transceiver 1 included in the optical transmission and reception system according to the fourth embodiment shown in Fig. 11 is obtained by adding a communication function unit 114 to the optical transceiver 1 included in the optical transmission and reception system according to the third embodiment shown in Fig. 9. The other configuration example of the optical transceiver 1 included in the optical transmission and reception system according to the fourth embodiment shown in Fig. 11 is the same as the configuration example of the optical transceiver 1 included in the optical transmission and reception system according to the third embodiment shown in Fig. 9, and the same reference numerals are used and only the different parts will be described.

[0068] The received signal obtained by the ADC 105 is output to the correlation processing unit 106 and the communication function unit 114 .

[0069] The communication function unit 114 outputs the calculation result by the difference calculation unit 109 as a communication signal (TX) to the selector 112. In addition, the communication function unit 114 acquires a communication signal (RX) from the opposing optical transceiver 1 from the received signal obtained by the ADC 105. Then, the communication function unit 114 outputs the acquired communication signal to the difference calculation unit 109.

[0070] In addition, the selector 112 outputs a signal indicating the pseudo-random code output by the pseudo-random code generator 101, a signal indicating the dummy code output by the dummy code generator 111, or a communication signal (TX) output by the communication function unit 114 to the transmitting side of the digital optical transceiver 110.

[0071] Here, when the selector 112 itself is performing measurement, it outputs a signal indicating the pseudo-random code output by the pseudo-random code generator 101 to the transmission side of the digital optical transceiver 110. That is, in this case, the selector 112 does not output the signal indicating the dummy code output by the dummy code generator 111 or the communication signal (TX) output by the communication function unit 114 to the transmission side of the digital optical transceiver 110. On the other hand, when the opposing optical transceiver 1 is performing measurement, the selector 112 outputs the signal indicating the dummy code output by the dummy code generator 111 to the transmission side of the digital optical transceiver 110. That is, in this case, the selector 112 does not output the signal indicating the pseudo-random code output by the pseudo-random code generator 101 or the communication signal (TX) output by the communication function unit 114 to the transmission side of the digital optical transceiver 110. On the other hand, when communicating with the counterpart optical transceiver 1, the selector 112 outputs the communication signal (TX) output by the communication function unit 114 to the transmitting side of the digital optical transceiver 110. In other words, in this case, the selector 112 does not output the signal indicating the pseudo-random code output by the pseudo-random code generator 101 or the signal indicating the dummy code output by the dummy code generator 111 to the transmitting side of the digital optical transceiver 110.

[0072] The transmitting side of the digital optical transceiver 110 generates transmission light based on the signal output by the selector 112 and outputs it to the optical circulator 103 .

[0073] In addition, the difference calculation unit 109 integrates the calculation results based on its own calculation results and the calculation results of the difference calculation unit 109 in the opposing optical transceiver 1, which is the communication signal (RX) acquired by the communication function unit 114.

[0074] The ADC 105 may always output the received signal to the correlation processing unit 106 and the communication function unit 114, or may switch the output destination to either the correlation processing unit 106 or the communication function unit 114 in response to switching of the selector 112. When the ADC 105 switches the output destination, it outputs the received signal to the correlation processing unit 106 when it is performing measurement, and outputs the received signal to the communication function unit 114 when it is communicating with the opposing optical transceiver 1.

[0075] Next, an example of operation of the optical transceiver system according to the fourth embodiment shown in FIG. 11 will be described with reference to FIG. 12. Below, an example of operation in the case where the first optical transceiver 1-1 and the second optical transceiver 1-2 function as a fiber-type radiation distribution meter will be described. First, one optical transceiver 1 measures the cumulative absorption dose distribution (step ST201). For example, the first optical transceiver 1-1 measures the cumulative absorption dose distribution. The measurement operation at this time is the same as the operation described in the third embodiment.

[0076] Thereafter, the other optical transceiver 1 measures the cumulative absorption line dose distribution (step ST202). For example, the second optical transceiver 1-2 measures the cumulative absorption line dose distribution. The measurement operation at this time is the same as the operation described in the third embodiment.

[0077] Then, after the first optical transceiver 1-1 and the second optical transceiver 1-2 have completed measuring the cumulative absorption ray amount distribution, one optical transceiver 1 acquires the measurement result from the other optical transceiver 1 (step ST203). For example, the first optical transceiver 1-1 acquires the measurement result from the second optical transceiver 1-2. At this time, the first optical transceiver 1-1 and the second optical transceiver 1-2 operate in communication mode, and the second optical transceiver 1-2 transmits data indicating the cumulative absorption ray amount distribution calculated by itself as a communication signal (TX), and the first optical transceiver 1-1 acquires the communication signal (RX). This allows the first optical transceiver 1-1 to acquire data indicating the cumulative absorption ray amount distribution calculated by the second optical transceiver 1-2.

[0078] Thereafter, one of the optical transceivers 1 integrates the absorption ray cumulative dose distributions (step ST204). For example, the first optical transceiver 1-1 integrates the absorption ray cumulative dose distributions. At this time, the first optical transceiver 1-1 integrates the absorption ray cumulative dose distribution calculated by itself with the absorption ray cumulative dose distribution calculated by the second optical transceiver 1-2.

[0079] 11, the coordinate of one end of the optical fiber 2 on the side of the first optical transceiver 1-1 is set to x=0, the coordinate of the other end of the optical fiber 2 on the side of the second optical transceiver 1-2 is set to x=L2, and the intermediate position therebetween is set to x=L1.

[0080] In this case, first, the first optical transceiver 1-1 calculates loss curve data as shown on the left side of Fig. 13, and the second optical transceiver 1-2 calculates loss curve data as shown on the right side of Fig. 13. In Fig. 13, reference numerals 131-1 and 131-2 indicate loss data (Lo(x)) before the installation of the optical fiber 2, and reference numerals 132-1 and 132-2 indicate loss curve data (L(x)). In the example of Fig. 13, the locations indicated by reference numerals 133-1 and 133-2 are locations where the optical power is significantly reduced and are locations that have been heavily exposed to radiation.

[0081] Thereafter, the first optical transceiver 1-1 calculates the loss curve differential data and the cumulative absorption ray amount distribution as shown on the left side of Fig. 14, and the second optical transceiver 1-2 calculates the loss curve differential data and the cumulative absorption ray amount distribution as shown on the right side of Fig. 14. In Fig. 14, reference numerals 141-1 and 141-2 indicate the loss curve differential data ({Lo(x)}') before the installation of the optical fiber 2, and reference numerals 142-1 and 142-2 indicate the loss curve differential data ({L(x)}'). In the example of Fig. 14, the locations indicated by reference numerals 143-1 and 143-2 are locations where the power is significantly reduced and are locations that have been heavily exposed to radiation.

[0082] Then, as shown in Fig. 15, the first optical transceiver 1-1 integrates the data by connecting the cumulative absorption ray amount distributions at the coordinates where the results are obtained by both the optical transceivers 1-1 and 1-2. In the example of Fig. 14, the first optical transceiver 1-1 and the second optical transceiver 1-2 both measure the cumulative absorption ray amount distributions at x = L1. Therefore, in this case, the first optical transceiver 1-1 can integrate the data by connecting the cumulative absorption ray amount distributions at x = L1. In Fig. 15, reference numeral 151 denotes the loss differential data ({Lo(x)}') (after integration) before the installation of the optical fiber 2, and reference numeral 152 denotes the loss curve differential data ({L(x)}') (after integration).

[0083] In the above example, the first optical transceiver 1-1 and the second optical transceiver 1-2 function as a fiber-type radiation distribution meter. However, the present invention is not limited to this example. When the first optical transceiver 1-1 and the second optical transceiver 1-2 measure optical loss, the optical loss may be integrated.

[0084] In the above description, the case where the communication function unit 114 is added to the optical transceiver 1 according to the third embodiment shown in Fig. 9 has been described. However, the present invention is not limited to this, and the communication function unit 114 and the selector 112 may be added to the optical transceiver 1 according to the second embodiment or the optical transceiver 1 according to the third embodiment shown in Fig. 10, and the same effects as those described above can be obtained.

[0085] In addition, when a communication function unit 114 and a selector 112 are added to the optical transceiver 1 of embodiment 2, that is, when a communication function unit 114 and a selector 112 are added to a configuration in which the gain of LA1043 is fixed using leakage light, when one optical transceiver 1 performs measurement, the other optical transceiver 1 sets the output of transmitted light to 0 or turns off the transmitting side of the digital optical transceiver 110.

[0086] As described above, according to the fourth embodiment, the optical transmission and reception system includes the communication function unit 114 that outputs data indicating the calculation result by the difference calculation unit 109 as a communication signal and acquires a communication signal from the optical transceiver 1 provided on the other end of the optical fiber 2 from the received signal obtained by the analog-to-digital converter 105, and the selector 112 that outputs a signal indicating the pseudo-random code generated by the pseudo-random code generator 101 or the communication signal output by the communication function unit 114, and the digital optical transmitter 102 generates and outputs transmission light based on the signal output by the selector 112, and the difference calculation unit 109 integrates the calculation results based on the calculation result and the communication signal acquired by the communication function unit 114. As a result, the optical transmission and reception system according to the fourth embodiment can improve the dynamic range of the measurement distance in addition to the effects of the optical transceiver 1 according to the second and third embodiments.

[0087] Finally, with reference to FIG. 16 , an example of a hardware configuration of the optical transceiver 1 according to the first to fourth embodiments will be described. Below, an example of a hardware configuration of the optical transceiver 1 according to the first embodiment will be described, but the same applies to the example of a hardware configuration of the optical transceiver 1 according to the second to fourth embodiments. The functions of the pseudo-random code generator 101, the ADC 105, the correlation processing unit 106, the loss curve data calculation unit, the differential processing unit 107, and the difference calculation unit 109 in the optical transceiver 1 are realized by a processing circuit 51. The processing circuit 51 may be dedicated hardware as shown in FIG. 16A , or may be a CPU (also referred to as a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, or DSP (Digital Signal Processor)) 52 that executes a program stored in a memory 53 as shown in FIG. 16B .

[0088] When the processing circuit 51 is dedicated hardware, the processing circuit 51 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The functions of each of the pseudorandom code generator 101, the ADC 105, the correlation processing unit 106, the loss curve data calculation unit, the differential processing unit 107, and the difference calculation unit 109 may be realized individually by the processing circuit 51, or the functions of each unit may be realized collectively by the processing circuit 51.

[0089] When the processing circuit 51 is a CPU 52, the functions of the pseudorandom code generator 101, the ADC 105, the correlation processing unit 106, the loss curve data calculation unit, the differential processing unit 107, and the difference calculation unit 109 are realized by software, firmware, or a combination of software and firmware. The software and firmware are written as programs and stored in the memory 53. The processing circuit 51 realizes the functions of each unit by reading and executing the programs stored in the memory 53. In other words, the optical transceiver 1 includes a memory for storing programs that, when executed by the processing circuit 51, result in the execution of, for example, each step shown in FIG. 2 . Furthermore, these programs can also be said to cause a computer to execute the procedures and methods of the pseudorandom code generator 101, the ADC 105, the correlation processing unit 106, the loss curve data calculation unit, the differential processing unit 107, and the difference calculation unit 109. Here, examples of the memory 53 include non-volatile or volatile semiconductor memories such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), and EEPROM (Electrically EPROM), as well as magnetic disks, flexible disks, optical disks, compact disks, minidisks, and DVDs (Digital Versatile Discs).

[0090] It is also possible to realize some of the functions of the pseudo-random code generator 101, the ADC 105, the correlation processing unit 106, the loss curve data calculation unit, the differential processing unit 107, and the difference calculation unit 109 with dedicated hardware and some of the functions with software or firmware. For example, the function of the pseudo-random code generator 101 can be realized by the processing circuit 51 as dedicated hardware, and the functions of the ADC 105, the correlation processing unit 106, the loss curve data calculation unit, the differential processing unit 107, and the difference calculation unit 109 can be realized by the processing circuit 51 reading out and executing programs stored in the memory 53.

[0091] In this way, the processing circuitry 51 can realize each of the above-described functions by hardware, software, firmware, or a combination of these.

[0092] It should be noted that the embodiments may be freely combined, or any of the components in each embodiment may be modified, or any of the components in each embodiment may be omitted.

[0093] The optical transceiver 1 according to the present disclosure is capable of measuring optical loss with higher distance resolution than conventional ones, and is suitable for use in optical transceivers that can measure optical loss.

[0094] 1 Optical transceiver, 1-1 First optical transceiver, 1-2 Second optical transceiver, 2 Optical fiber, 51 Processing circuit, 52 CPU, 53 Memory, 101 Pseudorandom code generator, 102 Digital optical transmitter, 103 Optical circulator (transmitter / receiver switch), 104 Analog optical receiver, 105 ADC (analog-to-digital converter), 106 Correlation processing unit, 107 Differential processing unit, 108 Differential data acquisition unit, 109 Difference calculation unit, 110 Digital optical transceiver, 111 Dummy code generator, 112 Selector, 113 Optical power adjustment unit, 114 Communication function unit, 1041 PD, 1042 TIA, 1043 LA.

Claims

1. A pseudorandom code generator that outputs a signal indicative of a pseudorandom code; a digital optical transmitter capable of transmitting at 1 Gbit or more that generates and transmits transmission light based on the signal indicative of the pseudorandom code output by the pseudorandom code generator; an analog optical receiver that receives input light as received light and converts the received light into a received signal; a transmit / receive switch that outputs the transmission light transmitted by the digital optical transmitter to one end of an optical fiber and outputs the light from the optical fiber to the analog optical receiver; an analog-to-digital converter that converts the received signal obtained by the analog optical receiver from an analog signal to a digital signal; a correlation processing unit that calculates loss curve data by performing correlation processing between the signal indicative of the pseudorandom code and the received signal based on the signal indicative of the pseudorandom code output by the pseudorandom code generator and the received signal obtained by the analog-to-digital converter; and a differentiation processing unit that calculates loss curve differentiation data by performing differentiation processing based on the loss curve data calculated by the correlation processing unit. and a difference calculation unit that calculates a difference between the loss differential data before the optical fiber is installed and the loss curve differential data calculated by the differential processing unit, based on the loss differential data.

2. The optical transceiver according to claim 1, wherein the digital optical transmitter is a digital optical transmitter that performs OOK modulation.

3. An optical transmitter / receiver as claimed in claim 1 or 2, characterized in that said digital optical transmitter and said analog optical receiver are constituted by a digital optical transceiver.

4. An optical transceiver as described in claim 3, characterized in that the receiving side of the digital optical transceiver has a limiting amplifier, and the transmit / receive switch outputs leakage light of the transmitted light transmitted by the transmitting side of the digital optical transceiver, which leakage light is capable of fixing the gain of the limiting amplifier, to the receiving side of the digital optical transceiver.

5. The optical transceiver according to claim 4, wherein the leakage light is -20 dB or more.

6. An optical transceiver as described in claim 3, characterized in that the receiving side of the digital optical transceiver has a limiting amplifier, and the transmit / receive switch outputs to the receiving side of the digital optical transceiver transmitted light based on a dummy code that is uncorrelated with the pseudo-random code used by the device itself, the transmitted light being input via the optical fiber from an optical transceiver provided at the other end of the optical fiber.

7. An optical transceiver as described in claim 6, further comprising: a dummy code generator that outputs a signal indicating a dummy code that is not correlated with the pseudo-random code used in an optical transceiver provided at the other end of the optical fiber; and a selector that outputs a signal indicating the pseudo-random code output by the pseudo-random code generator or a signal indicating the dummy code output by the dummy code generator, wherein the transmitting side of the digital optical transceiver generates and outputs transmission light based on the signal output by the selector.

8. The optical transceiver according to claim 6, characterized in that the pseudo-random code generator outputs a signal indicating a pseudo-random code or a signal indicating a dummy code that is uncorrelated with the pseudo-random code used in the optical transceiver provided at the other end of the optical fiber, and the transmitting side of the digital optical transceiver generates and outputs transmission light based on the signal output by the pseudo-random code generator.

9. An optical transceiver according to any one of claims 1 to 8, characterized in that the difference calculation section calculates a distribution of accumulated absorbed radiation amounts based on the calculated difference.

10. An optical transceiver as claimed in any one of claims 1 to 9, characterized in that it comprises: a communication function unit that outputs data indicating the calculation result by the difference calculation unit as a communication signal, and acquires a communication signal from the optical transceiver provided at the other end of the optical fiber from the received signal obtained by the analog-to-digital converter; and a selector that outputs a signal indicating a pseudo-random code generated by the pseudo-random code generator or a communication signal output by the communication function unit, wherein the digital optical transmitter generates and outputs transmission light based on the signal output by the selector, and the difference calculation unit integrates the calculation result based on the calculation result and the communication signal acquired by the communication function unit.

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