Optical transceiver

Abstract

A pseudo-random code generator (101) that outputs a signal indicating a pseudo-random code, a digital optical transmitter (102) capable of transmitting 1 Gbit or more that generates and transmits transmitted light based on the signal indicating the pseudo-random code, an analog optical receiver (104) that receives the input light as received light and converts it into a received signal, a transmission / reception switch that outputs the transmitted light to one end of an optical fiber (2) and outputs the light from the optical fiber (2) to the analog optical receiver (104), an ADC (105) that converts the received signal into a digital signal, a correlation processing unit (106) that calculates loss curve data by performing correlation processing between the signal indicating the pseudo-random code and the received signal obtained by the ADC (105), a differential processing unit (107) that calculates loss curve differential data by performing differential processing based on the loss curve data, and a difference calculation unit (109) that calculates the difference between the loss differential data before installation of the optical fiber (2) and the loss curve differential data.

Description

Technical Field

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

Background Art

[0002] Conventionally, an apparatus for obtaining radiation dose distribution information has been known (see, for example, Patent Document 1). In the apparatus disclosed in Patent Document 1, in order to obtain radiation dose distribution information along an optical fiber for a sensor, a single-pulse OTDR measurement method driven by a light source with a pulse width of tw and a pulse period of tp is used. This method estimates the radiation exposure dose by also using the wavelength dependence (difference) of the degradation amount due to radiation by performing OTDR processing on a plurality of wavelengths such as Stokes light and anti-Stokes light. Further, Patent Document 1 also describes that a pseudo-random pulse OTDR measurement method driven by a pulse train may be used.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

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

[0005] The present disclosure has been made to solve the above problems, and an object thereof is to provide an optical transceiver capable of measuring optical loss with high distance resolution as compared with the conventional art.

Means for Solving the Problems

[0006] The optical transceiver according to the present disclosure includes a pseudo-random number code generator that outputs a signal indicating a pseudo-random number code, a digital optical transmitter that generates and transmits transmitted light based on the signal indicating the pseudo-random number code output by the pseudo-random number code generator and is capable of transmitting 1 Gbit or more, an analog optical receiver that receives the input light as received light and converts the received light into a received signal, a transmission / reception switch that outputs the transmitted 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 from an analog signal to a digital signal based on the received signal obtained by the analog optical receiver, a correlation processing unit that calculates loss curve data by performing correlation processing between the signal indicating the pseudo-random number code and the received signal based on the signal indicating the pseudo-random number code output by the pseudo-random number code generator and the received signal obtained by the analog-to-digital converter, a differential processing unit that calculates loss curve differential data by performing differential processing based on the loss curve data calculated by the correlation processing unit, and a difference calculation unit that calculates the difference between the loss differential data before installation of the optical fiber and the loss curve differential data calculated by the differential processing unit. The digital optical transmitter and the analog optical receiver are composed of a digital optical transceiver. The receiving side of the digital optical transceiver has a limiting amplifier. The transmit-receive switch outputs, to the receiving side of the digital optical transceiver, the leakage light of the transmitted optical signal transmitted by the transmitting side of the digital optical transceiver, which can fix the gain of the limiting amplifier. It is characterized by the above.

Effects of the Invention

[0007] According to the present disclosure, since it is configured as described above, optical loss can be measured with high distance resolution as compared with the conventional art.

Brief Description of the Drawings

[0008]

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Embodiments for Carrying Out the Invention

[0009] Hereinafter, the embodiments will be described in detail with reference to the drawings. Embodiment 1. FIG. 1 is a diagram showing a configuration example of an optical transceiver 1 according to Embodiment 1. In FIG. 1, a case where the optical transceiver 1 is a fiber type radiation distribution meter that measures the absorption line cumulative amount distribution (radiation dose distribution) is shown as an example. In FIG. 1, a case where the optical fiber 2 is attached to an object to be measured irradiated with radiation via an adhesion means is shown as an example. In FIG. 1, a plurality of arrows shown above the optical fiber 2 indicate irradiation of radiation. This optical transceiver 1 is applicable, for example, in power plants such as satellites and nuclear reactors. For example, even when the optical transceiver 1 is applied in a place where people cannot enter, such as a nuclear reactor, the optical transceiver 1 can measure the absorption line cumulative amount distribution remotely.

[0010] As shown in FIG. 1, this optical transceiver 1 includes a pseudo-random number code generator 101, a digital optical transmitter 102, an optical circulator (transmission / reception 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. This optical transceiver 1 is provided on one end side of the optical fiber 2.

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

[0012] The digital optical transmitter 102 generates transmitted light based on a signal indicating the pseudo-random code output by the pseudo-random code generator 101 and transmits it to the optical circulator 103. The transmitted light generated by this digital optical transmitter 102 is continuous light. This digital optical transmitter 102 is a digital optical transmitter capable of transmitting at 1 Gbit or more.

[0013] As this digital optical transmitter 102, for example, an SFP (Small Form-factor Pluggable) can be used. Also, as the digital optical transmitter 102, it is not limited to SFP, and for example, a faster one such as SFP+, QSFP, SFP28, etc. may 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 transmitted light transmitted by the digital optical transmitter 102 to one end of the optical fiber 2. Also, the optical circulator 103 outputs the light (backscattered light) from the optical fiber 2 to the analog optical receiver 104.

[0015] In FIG. 1, the case where the optical circulator 103 is used as the transmit-receive switch is shown. However, the transmit-receive switch is not limited to this, and for example, an optical coupler may be used as the transmit-receive 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 this analog optical receiver 104 is output to the ADC 105.

[0017] As this analog optical receiver 104, for example, a PD (photodiode) can be used.

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

[0019] Note that, in order to improve the SNR of the received signal, the ADC 105 may obtain the received signal multiple times, perform an averaging process on the multiple received signals, and thus obtain the received signal to be output to the correlation processing unit 106.

[0020] Based on the signal indicating the pseudo-random code output by the pseudo-random code generator 101 and the received signal obtained by the ADC 105, the correlation processing unit 106 performs correlation processing between the signal indicating the pseudo-random code and the received signal to calculate loss curve data. This loss curve data is data indicating the optical loss in the distance direction along the optical fiber 2. The calculation of the loss curve data by this correlation processing unit 106 can apply a conventionally known calculation method, and its description is omitted. The loss curve data calculated by this correlation processing unit 106 is output to the differential processing unit 107.

[0021] Based on the loss curve data calculated by the correlation processing unit 106, the differential processing unit 107 performs differential processing to calculate loss curve differential data. This loss curve differential data is data indicating the change rate of the optical loss in the distance direction along the optical fiber 2. The loss curve differential data calculated by this differential processing unit 107 is output to the difference calculation unit 109.

[0022] The differential data acquisition unit 108 acquires loss differential data before the installation of the optical fiber 2. Note that the loss differential data is data indicating the change rate of the 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 this differential data acquisition unit 108 is output to the difference calculation 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. Also, when the optical transceiver 1 functions as a fiber type radiation distribution meter, the difference calculation unit 109 calculates the absorption line cumulative amount distribution based on the calculated difference. This absorption line cumulative amount distribution is a distribution indicating the radiation dose in the distance direction along the optical fiber 2.

[0024] Next, an operation example of the optical transceiver 1 according to Embodiment 1 shown in FIG. 1 will be described with reference to FIG. 2. That is, hereinafter, an operation example in the case where the optical transceiver 1 functions as a fiber type radiation distribution meter will be shown. In the operation example of the optical transceiver 1 according to Embodiment 1 shown in FIG. 1, for example, as shown in FIG. 2, first, the pseudo-random number code generator 101 generates a pseudo-random number code (step ST101). A signal indicating the pseudo-random number code generated by the pseudo-random number 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 transmitted light based on the signal indicating the pseudo-random number code output by the pseudo-random number code generator 101 and transmits it to the optical circulator 103, and the optical circulator 103 outputs the transmitted 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, and the analog optical receiver 104 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, ADC105 converts the received signal obtained by analog optical receiver 104 from an analog signal to a digital signal (step ST104). The received signal, which is the digital signal obtained by this ADC105, is output to correlation processing unit 106.

[0028] Next, correlation processing unit 106 calculates loss curve data by performing correlation processing between the signal indicating the pseudo-random code output by pseudo-random code generator 101 and the received signal obtained by ADC105 based on the signal indicating the pseudo-random code and the received signal (step ST105). The loss curve data calculated by this correlation processing unit 106 is output to differential processing unit 107.

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

[0030] Also, differential data acquisition unit 108 acquires loss differential data before the installation of optical fiber 2 (step ST107). The loss differential data acquired by this differential data acquisition unit 108 is output to difference calculation unit 109.

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

[0032] Figure 3 shows an example of loss data and loss curve data handled by optical transceiver 1 according to Embodiment 1. In FIG. 3, reference numeral 31 indicates loss data (Lo(x)) before the installation of the optical fiber 2, reference numeral 32 indicates loss curve data (L(x)), and reference numeral 33 indicates loss curve data (L(x)) when there is degradation of the optical devices (digital optical transmitter 102 and analog optical receiver 104). Also, in the example of FIG. 3, the portion indicated by reference numeral 34 is where the optical power has significantly decreased and is a highly exposed area. As shown in this FIG. 3, in the loss curve data when there is degradation of the optical devices indicated by reference numeral 33, the optical power has decreased overall with the degradation of the optical devices compared to the loss curve data when there is no degradation of the optical devices indicated by reference numeral 32.

[0033] FIG. 4 shows an example of loss differential data, loss curve differential data, and absorption line cumulative amount distribution handled by the optical transceiver 1 according to Embodiment 1. In FIG. 4, reference numeral 41 indicates loss differential data ({Lo(x)}’) before the installation of the optical fiber 2, reference numeral 42 indicates loss curve differential data ({L(x)}’), and reference numeral 43 indicates loss curve differential data ({L(x)}’) when there is degradation of the optical devices. Also, in the example of FIG. 4, the portion indicated by reference numeral 44 is where the power has significantly decreased and is a highly exposed area. Also, as shown in FIG. 4, the absorption line cumulative amount distribution is E(x)=S{Lo(x)-L(x)}’. Here, S is a coefficient ([Gy / (dB / m)]) indicating the relationship between the degradation amount of the optical fiber 2 for the sensor and the radiation dose, which is measured in advance. As shown in this FIG. 4, in the loss curve differential data when there is degradation of the optical devices indicated by reference numeral 43, there is no change regardless of the degradation of the optical devices compared to the loss curve differential data when there is no degradation of the optical devices indicated by reference numeral 42.

[0034] In this way, in the optical transceiver 1 according to Embodiment 1, by taking the difference between the loss differential data and the loss curve differential data before the installation of the optical fiber 2, it is possible to measure the optical loss and the radiation dose distribution without being affected by the degradation of the optical device due to radiation irradiation. That is, in the optical transceiver 1 according to Embodiment 1, 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 radiation dose do not change depending on the presence or absence of degradation of the optical device.

[0035] Also, in the prior art, the resolution was restricted by the size of the optical fiber 2 and the pulse width of the transmitted light. On the other hand, in the optical transceiver 1 according to Embodiment 1, high-resolution data corresponding to the bit rate of the digital optical transmitter 102 can be obtained. Therefore, in the optical transceiver 1 according to Embodiment 1, it is possible to detect an increase in the local exposure dose or the like by differential processing.

[0036] As described above, according to the first embodiment, the optical transceiver 1 includes a pseudo-random code generator 101 that outputs a signal indicating a pseudo-random code, a digital optical transmitter 102 that can transmit at 1 Gbit or more and generates and transmits transmission light based on the signal indicating the pseudo-random code output by the pseudo-random code generator 101, an analog optical receiver 104 that receives the input light as received light and converts the received light into a received 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, an ADC 105 that converts the received signal obtained by the analog optical receiver 104 from an analog signal to a digital signal based on the received signal, a correlation processing unit 106 that calculates loss curve data by performing correlation processing between the signal indicating the pseudo-random code output by the pseudo-random code generator 101 and the received signal obtained by the ADC 105, a differential processing unit 107 that calculates loss curve differential data by performing differential processing based on the loss curve data calculated by the correlation processing unit 106, and a difference calculation unit 109 that calculates the difference between the loss differential data before the installation of the optical fiber 2 and the loss curve differential data calculated by the differential processing unit 107. Also, according to the first embodiment, the digital optical transmitter 102 is a digital optical transmitter that performs OOK modulation. As a result, the optical transceiver 1 according to the first embodiment can measure optical loss with high distance resolution compared to the prior art.

[0037] Also, according to the first embodiment, the difference calculation unit 109 may calculate the absorption line cumulative amount distribution based on the calculated difference. As a result, the optical transceiver 1 according to the first embodiment can measure the radiation dose distribution with high distance resolution compared to the prior art.

[0038] Second Embodiment. FIG. 5 is a diagram showing a configuration example of the optical transceiver 1 according to Embodiment 2. The optical transceiver 1 according to Embodiment 2 shown in FIG. 5 is such that the digital optical transmitter 102 and the analog optical receiver 104 in the optical transceiver 1 according to Embodiment 1 shown in FIG. 1 are constituted by a digital optical transceiver 110. Regarding other configuration examples in the optical transceiver 1 according to Embodiment 2 shown in FIG. 5, they are the same as the configuration example of the optical transceiver 1 according to Embodiment 1, and only the different parts will be described with the same reference numerals.

[0039] On the transmission side of the digital optical transceiver 110, transmission light is generated based on a signal indicating a pseudo-random code output by the pseudo-random code generator 101 and output to the optical circulator 103. Also, on the reception side of the digital optical transceiver 110, light (backscattered light and leakage light) from the optical circulator 103 is received as reception light, and the reception light is converted into a reception signal. The reception signal obtained by the reception side of this digital optical transceiver 110 is output to the ADC 105. Also, on the reception side of the digital optical transceiver 110, the gain of the LA 1043 described later is fixed by the leakage light from the optical circulator 103. This digital optical transceiver 110 is a digital optical transceiver capable of transmitting 1 Gbit or more.

[0040] As this digital optical transceiver 110, for example, the transmission port and reception port of an SFP can be used. Also, the digital optical transceiver 110 is not limited to an SFP, and a faster one such as an SFP+, QSFP, SFP28, etc. may be used, as long as it is a digital optical transceiver that performs OOK digital modulation. As this digital optical transceiver 110, for example, a digital optical transceiver for PAM4 (4 Pulse Amplitude Modulation) can be used.

[0041] Note that the optical circulator 103 outputs, to the receiving side of the digital optical transceiver 110, the leakage light of the transmitted light transmitted by the transmitting side of the digital optical transceiver 110, which can fix the gain of LA1043. Note that the above leakage light is, for example, -20 dB or more.

[0042] Also, for example, as shown in FIG. 6, the receiving side in the digital optical transceiver 110 generally includes a PD1041, a TIA (trans-impedance amplifier) 1042, and an LA (limiting amplifier) 1043.

[0043] The PD1041 receives the light from the optical circulator 103 as received light and converts the received light into an electrical signal. The electrical signal obtained by the PD1041 is output to the TIA1042. The TIA1042 converts the current of the electrical signal into a voltage based on the electrical signal after conversion by the PD1041. The electrical signal after conversion by the TIA1042 is output to the LA1043. The LA1043 performs limiting on the electrical signal based on the electrical signal after conversion by the TIA1042. The electrical signal after processing by the LA1043 is output to the ADC105 as a received signal.

[0044] Here, the gain of the LA1043 increases or decreases according to the average optical power, and it operates so as to saturate the voltage amplitude of the input electrical signal with that gain. On the other hand, the leakage light is the transmitted light modulated by a pseudo-random code that has received a certain loss, and there is no time variation in the average power. Therefore, by inputting this leakage light to the LA1043, the gain of the LA1043 is determined according to the average power of the leakage light. As a result, the Rayleigh scattering component that does not significantly contribute to the average power below the leakage light is 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 indicates the output power from the TIA1042 of the leakage light component, reference numeral 72 indicates the output power from the TIA1042 of the Rayleigh scattering component when the detection time is t1, and reference numeral 73 indicates the output power from the TIA1042 of the Rayleigh scattering component when the detection time is t2 (≠t1). Further, reference numeral 74 indicates the output power from the LA1043 of the leakage light component, and the LA1043 outputs leakage light of a constant power. Also, reference numeral 75 indicates the output power from the LA1043 of the Rayleigh scattering component when the detection time is t1, and reference numeral 76 indicates the output power from the LA1043 of the Rayleigh scattering component when the detection time is t2. As shown on the left side of this FIG. 7, the leakage light constantly input to the receiving side in the digital optical transceiver 110 has a larger input power than the Rayleigh scattering component. Therefore, in the LA1043, the gain (G) is fixed to the gain that saturates this leakage 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 the detection time, and become analog values.

[0046] On the other hand, as shown on the right side of FIG. 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 shown by reference numeral 77). Therefore, for the time when the correlation value between the leakage light component and the pseudo-random number code is low, the Rayleigh scattering component can be detected, and the loss curve data can be obtained correctly. Note that on the right side of FIG. 7, reference numeral 78 indicates the noise level due to the leakage light.

[0047] In this way, by fixing the gain of the LA1043 by the leakage light component, the loss curve data can be obtained more correctly. On the other hand, in the optical transceiver 1 according to the second embodiment, when the leakage light component is small or there is no leakage light component, the assumed operation cannot be performed.

[0048] That is, as shown on the left side of FIG. 8, when the leakage light component is small or there is no leakage light component, in LA1043, when the detection time is t1, the gain (G1) is fixed to the 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 the 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 powers of the Rayleigh scattering component when the detection time is t1 and the Rayleigh scattering component when the detection time is t2 become almost the same, the loss change disappears, and the loss curve cannot be obtained correctly. In FIG. 8, reference numeral 81 indicates the output power from LA1043 of the Rayleigh scattering component when the detection times are t1 and t2.

[0049] Regarding operation examples other than the above in the optical transceiver 1 according to Embodiment 2, they are the same as the operation examples in the optical transceiver 1 according to Embodiment 1.

[0050] As described above, according to this Embodiment 2, the digital optical transmitter 102 and the analog optical receiver 104 are constituted by the digital optical transceiver 110. The receiving side of the digital optical transceiver 110 has LA1043, and the transmit / receive switch outputs, to the receiving side of the digital optical transceiver 110, the leakage light of the transmitted light transmitted by the transmitting side of the digital optical transceiver 110, which is leakage light capable of fixing the gain of LA1043. Also, according to Embodiment 2, the leakage light is -20 dB or more. Thereby, in addition to the effects of the optical transceiver 1 according to Embodiment 1, the optical transceiver 1 according to Embodiment 2 can use an inexpensive digital optical transceiver 110 as the digital optical transmitter 102 and the analog optical receiver 104, so that the optical transceiver 1 can be configured at low cost.

[0051] Embodiment 3. In Embodiment 2, the case where the gain of LA1043 is fixed using leakage light was shown. In contrast, in Embodiment 3, the case where the gain of LA1043 is fixed using the transmitted light (dummy light) transmitted from the optical transceiver 1 at the opposite end is shown.

[0052] FIG. 9 is a diagram showing a configuration example of an optical transceiver system according to Embodiment 3. 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 are optical transceivers 1 having the same configuration. The first optical transceiver 1-1 and the second optical transceiver 1-2 are arranged opposite to each other via an optical fiber 2. That is, the first optical transceiver 1-1 is provided on one end side of the optical fiber 2, and the second optical transceiver 1-2 is provided on the other end side of the optical fiber 2. In FIG. 9, the detailed configuration of the second optical transceiver 1-2 is not shown.

[0053] In the optical transceiver 1 included in the optical transceiver system according to Embodiment 3 shown in FIG. 9, compared with the optical transceiver 1 according to Embodiment 1 shown in FIG. 1, the digital optical transmitter 102 and the analog optical receiver 104 are constituted by a digital optical transceiver 110, and a dummy code generator 111, a selector 112, and an optical power adjuster 113 are added. Other configuration examples of the optical transceiver 1 included in the optical transceiver system according to Embodiment 3 shown in FIG. 9 are the same as the configuration example of the optical transceiver 1 according to Embodiment 1 shown in FIG. 1, and only the different parts are described with the same reference numerals.

[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 optical transceiver 1 at the opposite end. A signal indicating the dummy code generated by the dummy code generator 111 is output to the selector 112.

[0055] Selector 112 outputs a signal indicating a pseudo-random code output by the pseudo-random code generator 101 or a signal indicating a dummy code output by the dummy code generator 111 to the transmission side of the digital optical transceiver 110.

[0056] Here, when the measurement is performed by the own device, selector 112 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, 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 measurement is performed by the optical transceiver 1 of the opposite party, 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, 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 transmission side of the digital optical transceiver 110 generates transmission light based on the signal output by selector 112 and outputs it to the optical circulator 103. When the digital optical transceiver 110 generates transmission light modulated by the dummy code output by the dummy code generator 111, this transmission light is also referred to as dummy light. Also, when the dummy code is a code consisting entirely of "1", the dummy light becomes CW light. In addition, the reception 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 reception side of this digital optical transceiver 110 is output to the ADC 105. Also, the reception side of the digital optical transceiver 110 fixes the gain of the LA 1043 with the dummy light from the optical circulator 103. This digital optical transceiver 110 is a digital optical transceiver capable of transmitting 1 Gbit or more.

[0058] As this digital optical transceiver 110, for example, the transmission port and reception port of SFP can be used. Also, as the digital optical transceiver 110, not limited to SFP, a faster one such as SFP+, QSFP, SFP28, etc. may be used, as long as it is a digital optical transceiver that performs OOK digital modulation. As this digital optical transceiver 110, for example, a digital optical transceiver for PAM4 can be used.

[0059] The configuration itself of this digital optical transceiver 110 is the same as the configuration of the digital optical transceiver 110 shown in Embodiment 2.

[0060] The optical power adjustment unit 113 adjusts the optical power of the transmission optical signal on the transmission side of the digital optical transceiver 110. Note that the optical power adjustment unit 113 is not an essential configuration of the optical transceiver 1 and may not be provided in the optical transceiver 1.

[0061] Note that in FIG. 9, a case is shown where a dummy code generator 111 that generates a dummy code is provided in the optical transceiver 1 separately from the pseudo-random code generator 101. However, not limited to this, for example, as shown in FIG. 10, the dummy code generator 111 is not provided in the optical transceiver 1, and in the pseudo-random code generator 101, in addition to the pseudo-random code, a dummy code that has no correlation with the pseudo-random code in the opposite optical transceiver 1 may be generated. In this case, as shown in FIG. 10, the selector 112 is not required in the optical transceiver 1.

[0062] In the case of the configuration shown in FIG. 10, when the measurement is performed by the own device, the pseudo-random code generator 101 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 counterparty's optical transceiver 1 performs measurement, the pseudo-random number signal 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 number signal generator 101 does not generate a pseudo-random number code.

[0063] Next, an operation example of the optical transceiver system according to Embodiment 3 will be described. Here, the 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 is the basis of this dummy light is a dummy code that has no correlation with the pseudo-random number code used in the first optical transceiver 1-1. Then, the first optical transceiver 1-1 fixes the gain of the LA1043 possessed by the receiving side of its own digital optical transceiver 110 with the dummy light from the second optical transceiver 1-2. That is, in the optical transceiver system according to Embodiment 3, the gain of the LA1043 is fixed using dummy light without using the leakage light as shown in Embodiment 2.

[0064] If the level of the dummy light is too high, the noise floor may become high after the correlation process and measurement may become impossible. Therefore, in such a case, the optical power adjustment unit 113 adjusts to reduce the optical power of the digital optical transceiver 110 to an adjustable level.

[0065] Regarding the operation examples other than the above in the optical transceiver 1 according to Embodiment 3, they are the same as the operation examples in the optical transceiver 1 according to Embodiment 1.

[0066] As described above, according to the third embodiment, the digital optical transmitter 102 and the analog optical receiver 104 are constituted by the digital optical transceiver 110. The receiving side of the digital optical transceiver 110 has LA1043, and the transmission / reception switch outputs, to the receiving side of the digital optical transceiver 110, the transmission light from the optical transceiver 1 provided at the other end of the optical fiber 2 input via the optical fiber 2, which is the transmission light based on a dummy code having no correlation with the pseudo-random code used by the own device. Further, according to the third embodiment, there are provided a dummy code generator 111 that outputs a signal indicating a dummy code having no correlation 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. The transmitting side of the digital optical transceiver 110 generates and outputs transmission 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 having no correlation with the pseudo-random code used by 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. Thereby, in addition to the effects of the optical transceiver 1 according to the first embodiment, the optical transceiver 1 according to the third embodiment can use an inexpensive digital optical transceiver 110 as the digital optical transmitter 102 and the analog optical receiver 104, so that the optical transceiver 1 can be configured at low cost. Further, the optical transmission / reception system according to the third embodiment can relax the specification requirements such as the leakage light level in the transmission / reception switch for the optical transceiver 1 according to the second embodiment, and can improve the level adjustment performance of the optical transceiver 1.

[0067] Embodiment 4. FIG. 11 is a diagram showing a configuration example of an optical transmission / reception system according to the fourth embodiment. The optical transceiver 1 included in the optical transmission / reception system according to Embodiment 4 shown in FIG. 11 has an additional communication function unit 114 compared to the optical transceiver 1 included in the optical transmission / reception system according to Embodiment 3 shown in FIG. 9. Regarding other configuration examples of the optical transceiver 1 included in the optical transmission / reception system according to Embodiment 4 shown in this FIG. 11, they are the same as the configuration example of the optical transceiver 1 included in the optical transmission / reception system according to Embodiment 3 shown in FIG. 9, and only the different parts will be described with the same reference numerals.

[0068] Note that 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 differential calculation unit 109 as a communication signal (TX) to the selector 112. Also, the communication function unit 114 acquires a communication signal (RX) from the opposite 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 differential calculation unit 109.

[0070] Note that 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 the communication signal (TX) output by the communication function unit 114 to the transmission side of the digital optical transceiver 110.

[0071] Here, when the own device performs measurement, the selector 112 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 and the communication signal (TX) output by the communication function unit 114 to the transmission side of the digital optical transceiver 110. Also, when the counterparty 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 the signal indicating the pseudo-random number code output by the pseudo-random number code generator 101 and 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 counterparty optical transceiver 1, the selector 112 outputs the communication signal (TX) output by the communication function unit 114 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 number code output by the pseudo-random number code generator 101 and the signal indicating the dummy code output by the dummy code generator 111 to the transmission side of the digital optical transceiver 110.

[0072] Also, the transmission 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] Also, 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 counterparty optical transceiver 1, which is the communication signal (RX) acquired by the communication function unit 114.

[0074] Note that 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 the correlation processing unit 106 or the communication function unit 114 according to the switching of the selector 112 and then output. When the ADC 105 switches the output destination, when the local device performs measurement, it outputs the received signal to the correlation processing unit 106, and when communicating with the counterparty optical transceiver 1, it outputs the received signal to the communication function unit 114.

[0075] Next, an operation example of the optical transmission / reception system according to Embodiment 4 shown in FIG. 11 will be described with reference to FIG. 12. Hereinafter, an operation example in the case where the first optical transmission / reception unit 1-1 and the second optical transmission / reception unit 1-2 function as a fiber type radiation distribution meter will be shown. First, one of the optical transmission / reception units 1 measures the cumulative absorption line amount distribution (step ST201). For example, the first optical transmission / reception unit 1-1 measures the cumulative absorption line amount distribution. The measurement operation at this time is the same as the operation shown in Embodiment 3.

[0076] Thereafter, the other optical transmission / reception unit 1 measures the cumulative absorption line amount distribution (step ST202). For example, the second optical transmission / reception unit 1-2 measures the cumulative absorption line amount distribution. The measurement operation at this time is the same as the operation shown in Embodiment 3.

[0077] After the measurement of the cumulative absorption line amount distribution is completed in the first optical transmission / reception unit 1-1 and the second optical transmission / reception unit 1-2, one of the optical transmission / reception units 1 acquires the measurement result by the other optical transmission / reception unit 1 (step ST203). For example, the first optical transmission / reception unit 1-1 acquires the measurement result by the second optical transmission / reception unit 1-2. At this time, the first optical transmission / reception unit 1-1 and the second optical transmission / reception unit 1-2 operate in the communication mode, the second optical transmission / reception unit 1-2 transmits data indicating the cumulative absorption line amount distribution calculated by itself as a communication signal (TX), and the first optical transmission / reception unit 1-1 acquires the communication signal (TX) as a communication signal (RX). Thereby, the first optical transmission / reception unit 1-1 can acquire data indicating the cumulative absorption line amount distribution by the second optical transmission / reception unit 1-2.

[0078] Thereafter, one of the optical transmission / reception units 1 integrates the cumulative absorption line amount distribution (step ST204). For example, the first optical transmission / reception unit 1-1 integrates the cumulative absorption line amount distribution. At this time, the first optical transmission / reception unit 1-1 integrates the cumulative absorption line amount distribution calculated by itself and the cumulative absorption line amount distribution calculated by the second optical transmission / reception unit 1-2.

[0079] Here, for example, as shown in FIG. 11, the coordinate of one end of the optical fiber 2 on the side of the first optical transceiver 1-1 is set as x = 0, and the coordinate of the other end of the optical fiber 2 on the side of the second optical transceiver 1-2 is set as x = L2. Also, the intermediate position is set as 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 this example of FIG. 13, the locations indicated by reference numerals 133-1 and 133-2 are where the optical power is significantly decreased and are locations of heavy exposure.

[0081] Thereafter, the first optical transceiver 1-1 calculates loss curve differential data and absorption line cumulative amount distribution as shown on the left side of FIG. 14, and the second optical transceiver 1-2 calculates loss curve differential data and absorption line cumulative amount distribution as shown on the right side of FIG. 14. In FIG. 14, reference numerals 141-1 and 141-2 indicate loss differential data ({Lo(x)}’) before the installation of the optical fiber 2, and reference numerals 142-1 and 142-2 indicate loss curve differential data ({L(x)}’). In this example of FIG. 14, the locations indicated by reference numerals 143-1 and 143-2 are where the power is significantly decreased and are locations of heavy exposure.

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

[0083] In the above description, an operation example 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 has been shown. However, the present invention is not limited to this, and when the first optical transceiver 1-1 and the second optical transceiver 1-2 measure the 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 shown. 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 described above can be obtained.

[0085] When adding the communication function unit 114 and the selector 112 to the optical transceiver 1 according to the second embodiment, that is, when adding the communication function unit 114 and the selector 112 to the configuration in which the gain of LA1043 is fixed using the leakage light, when one of the optical transceivers 1 performs measurement, the other optical transceiver 1 shall set the output of the transmitted light to 0, or set the transmission side of the digital optical transceiver 110 to the off state.

[0086] As described above, according to the fourth embodiment, data indicating the calculation result by the difference calculation unit 109 is output as a communication signal, and from the received signal obtained by the analog-to-digital converter 105, a communication signal from the optical transceiver 1 provided on the other end side of the optical fiber 2 is acquired. A communication function unit 114, and a 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. The digital optical transmitter 102 generates and outputs transmission light based on the signal output by the selector 112. The difference calculation unit 109 integrates the calculation results based on the calculation results and the communication signals acquired by the communication function unit 114. Thereby, 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 in the optical transceivers 1 according to the second and third embodiments.

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

[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 pseudo-random number 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 by the processing circuit 51 respectively, or the functions of each unit may be realized together by the processing circuit 51.

[0089] When the processing circuit 51 is the CPU 52, the functions of the pseudo-random number 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 described 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. That is, the optical transceiver 1 includes a memory for storing a program that, when executed by the processing circuit 51, causes each step shown in, for example, FIG. 2 to be executed as a result. Also, these programs can be said to cause a computer to execute the procedures and methods of the pseudo-random number 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), magnetic disks, flexible disks, optical disks, compact disks, mini disks, or DVDs (Digital Versatile Discs).

[0090] Note that, regarding the functions of the pseudo-random number code generator 101, ADC 105, correlation processing unit 106, loss curve data calculation unit, differential processing unit 107, and difference calculation unit 109, part of them may be realized by dedicated hardware and part of them may be realized by software or firmware. For example, for the pseudo-random number code generator 101, its function can be realized by a processing circuit 51 as dedicated hardware, and for the ADC 105, correlation processing unit 106, loss curve data calculation unit, differential processing unit 107, and difference calculation unit 109, their functions can be realized by the processing circuit 51 reading and executing a program stored in the memory 53.

[0091] In this way, the processing circuit 51 can realize the above-mentioned respective functions by hardware, software, firmware, or a combination thereof.

[0092] Note that free combinations of each embodiment, or modifications of any component of each embodiment, or omission of any component in each embodiment are possible.

Industrial Applicability

[0093] The optical transceiver 1 according to the present disclosure can measure optical loss with high distance resolution compared to the prior art, and is suitable for use in an optical transceiver 1 capable of measuring optical loss and the like.

Explanation of Signs

[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 number code generator, 102 Digital optical transmitter, 103 Optical circulator (transmission / reception switch), 104 Analog optical receiver, 105 ADC (Analog-to-digital converter), 106 Correlation processing unit, 107 Differentiation processing unit, 108 Differentiated 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

A pseudo-random code generator that outputs a signal indicating a pseudo-random code, A digital optical transmitter capable of transmitting 1 Gbit or more, which generates and transmits transmission light based on a signal indicating a pseudo-random code output by the pseudo-random code generator, An analog optical receiver that receives the input light as received light and converts the received light into a received 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 the analog optical receiver, An analog-to-digital converter that converts the received signal from an analog signal to a digital signal based on the received signal obtained by the analog optical receiver, A correlation processing unit that calculates loss curve data by performing correlation processing between the signal indicating the pseudo-random code output by the pseudo-random code generator and the received signal obtained by the analog-to-digital converter, A differential processing unit that calculates loss curve differential data by performing differential processing based on the loss curve data calculated by the correlation processing unit, A difference calculation unit that calculates the difference between the loss differential data before the installation of the optical fiber and the loss curve differential data calculated by the differential processing unit, The digital optical transmitter and the analog optical receiver are constituted by a digital optical transceiver, The receiving side of the digital optical transceiver has a limiting amplifier, The transmission / reception switch outputs, to the receiving side of the digital optical transceiver, leakage light of the transmission light transmitted by the transmitting side of the digital optical transceiver, which can fix the gain of the limiting amplifier, An optical transceiver characterized by the above. A pseudo-random code generator that outputs a signal indicating a pseudo-random code, A digital optical transmitter capable of transmitting at 1 Gbit or more, which generates and transmits transmission light based on a signal indicating a pseudo-random code output by the pseudo-random code generator. An analog optical receiver that receives the 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 the analog optical receiver. An analog-to-digital converter that converts the reception signal from an analog signal to a digital signal based on the reception signal obtained by the analog optical receiver. A correlation processing unit that calculates loss curve data by performing correlation processing between the signal indicating the pseudo-random code output by the pseudo-random code generator and the reception signal based on the reception signal obtained by the analog-to-digital converter. A differential processing unit that calculates loss curve differential data by performing differential processing based on the loss curve data calculated by the correlation processing unit. A difference calculation unit that calculates the difference between the loss differential data before installation of the optical fiber and the loss curve differential data calculated by the differential processing unit, based on the loss differential data before installation of the optical fiber and the loss curve differential data calculated by the differential processing unit. The digital optical transmitter and the analog optical receiver are constituted by a digital optical transceiver. The reception side of the digital optical transceiver has a limiting amplifier. The transmission / reception switch outputs, to the reception side of the digital optical transceiver, transmission light based on a dummy code that is not correlated with the pseudo-random code used by itself, which is the transmission light from an optical transceiver provided on the other end side of the optical fiber input via the optical fiber. An optical transceiver characterized by the above.

3. The digital optical transmitter is a digital optical transmitter that performs OOK modulation. The optical transceiver according to claim 1 or claim 2, characterized by the above.

4. The leakage light is -20 dB or more. The optical transceiver according to claim 1, characterized in that.

5. A dummy code generator that outputs a signal indicating a dummy code that has no correlation with the pseudo-random code used in the optical transceiver provided on the other end side of the optical fiber; 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; The transmission side of the digital optical transceiver generates and outputs transmission light based on the signal output by the selector. The optical transceiver according to claim 2, characterized in that.

6. The pseudo-random code generator outputs a signal indicating a pseudo-random code or a signal indicating a dummy code that has no correlation with the pseudo-random code used in the optical transceiver provided on the other end side of the optical fiber, The transmission side of the digital optical transceiver generates and outputs transmission light based on the signal output by the pseudo-random code generator. The optical transceiver according to claim 2, characterized in that.

7. The difference calculation unit calculates the absorption line cumulative amount distribution based on the calculated difference. The optical transceiver according to claim 1 or claim 2, characterized in that.

8. 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 on the other end side of the optical fiber from the received signal obtained by the analog-to-digital converter; A selector that outputs a signal indicating the pseudo-random code generated by the pseudo-random code generator or a communication signal output by the communication function unit; The digital optical transmitter generates and outputs transmission light based on the signal output by the selector. The difference calculation unit integrates the calculation results based on the calculation results and the communication signals acquired by the communication function unit. The optical transceiver according to claim 1 or 2, characterized in that it is configured as described above.

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