Optical fiber delay measurement device

Abstract

The present invention provides an optical fiber delay measurement device, which belongs to the field of optical fiber measurement technology. The optical fiber delay measurement device includes: a pulse transmitter, which is used to generate a start pulse signal; an optical transmitter, which is used to transmit a dark pulse optical signal to the optical fiber under test according to the pulse signal; an optical receiver, which is used to receive the optical pulse signal output by the optical fiber under test and generate a stop pulse signal according to the optical pulse signal; a clock unit, which is used to generate a clock signal; a time digital converter, which is used to perform timing according to the start pulse signal, the clock signal and the stop pulse signal to obtain a time digital signal. A control unit is used to determine the optical fiber delay value according to the digital signal. The start pulse signal is modulated by a dark pulse method, so that the stop pulse signal does not change with the attenuation of the optical fiber under test, thereby improving the measurement accuracy of the optical fiber delay.

Description

Technical Field

[0001] The invention relates to the technical field of optical fiber measurement, and in particular to an optical fiber delay measurement device. Background Art

[0002] At present, the main methods for measuring fiber delay are pulse measurement, phase measurement and optical interference measurement. Among them, the pulse measurement method can use the time-to-digital conversion circuit in the mature ToF (time of flight) measurement technology, making the measurement device simple and low-cost. However, due to the change in the attenuation of the measured optical fiber, the level of the received optical pulse measurement signal also changes, resulting in inaccurate time position of the rising edge of the regenerated pulse signal, which seriously restricts the accuracy of fiber delay measurement. Therefore, it is necessary to improve the current scheme to obtain better time measurement accuracy. Summary of the invention

[0003] The purpose of the present invention is to provide a fiber optic delay measurement device, which can improve the accuracy of fiber optic delay measurement.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] An optical fiber delay measurement device, the optical fiber delay measurement device comprising:

[0006] A pulse transmitter, used for generating a start pulse signal;

[0007] An optical transmitter, connected to the pulse transmitter and one end of the optical fiber under test, and used to transmit a dark pulse optical signal to the optical fiber under test according to the pulse signal;

[0008] an optical receiver connected to the other end of the optical fiber under test, and configured to receive the optical pulse signal output by the optical fiber under test, and generate a stop pulse signal according to the optical pulse signal;

[0009] A clock unit, used for generating a clock signal;

[0010] A time digital converter, connected to the pulse transmitter, the optical receiver and the clock unit respectively, for timing according to the start pulse signal, the clock signal and the stop pulse signal to obtain a time digital signal;

[0011] A control unit is connected to the time digital converter and is used to determine the optical fiber delay value according to the time digital signal.

[0012] Optionally, the optical transmitter includes:

[0013] A pulse signal shaping circuit, connected to the pulse transmitter, for shaping the start pulse signal to obtain a shaped pulse signal;

[0014] A laser current driving circuit, connected to the pulse signal shaping circuit, for generating a driving current according to the shaped pulse signal;

[0015] The laser assembly is connected to the laser current driving circuit and one end of the optical fiber under test respectively, and is used to generate a dark pulse light signal according to the driving current and output it to the optical fiber under test.

[0016] Optionally, the laser assembly comprises:

[0017] A laser, connected to the laser current driving circuit and one end of the optical fiber under test, respectively, for generating a dark pulse light signal according to the driving current and outputting it to the optical fiber under test;

[0018] A back-light detector, arranged on the laser, for detecting the optical power of the dark pulse optical signal generated by the laser;

[0019] The automatic power control circuit is connected to the backlight detector and the laser current driving circuit respectively, and is used for controlling the driving current output by the laser current driving circuit according to the optical power.

[0020] Optionally, the optical transmitter further includes:

[0021] a thermistor, disposed on the laser and used to detect the temperature of the laser;

[0022] An automatic temperature control circuit, connected to the thermistor, for generating a temperature control signal according to the temperature of the laser;

[0023] The semiconductor refrigerator is arranged on the laser and connected to the automatic temperature control circuit, and is used for cooling or heating according to the temperature control signal.

[0024] Optionally, the laser is a semiconductor laser.

[0025] Optionally, the semiconductor laser component is a distributed feedback semiconductor laser.

[0026] Optionally, the optical receiver includes:

[0027] A photoelectric detector connected to the other end of the optical fiber under test, used to detect the optical pulse signal output by the optical fiber under test and convert the optical pulse signal into an electrical signal;

[0028] a preamplifier, connected to the photodetector, and used to amplify the electrical signal to obtain a first amplified electrical signal;

[0029] a controllable gain amplifier, connected to the preamplifier, and configured to amplify the first amplified electrical signal to obtain a second amplified electrical signal;

[0030] an automatic gain control circuit, connected to the controllable gain amplifier, and configured to adjust the gain of the controllable gain amplifier according to the second amplified electrical signal;

[0031] The comparison amplifier is connected to the controllable gain amplifier and the time-to-digital converter respectively, and is used to compare the second amplified electrical signal with the threshold level, perform signal regeneration, and obtain a stop pulse signal.

[0032] Optionally, the preamplifier is a transimpedance amplifier.

[0033] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: a start pulse signal is generated by a pulse transmitter, the optical transmitter modulates the start pulse signal by a dark pulse method, and transmits a dark pulse optical signal to the optical fiber under test, the optical receiver receives the optical pulse signal output by the optical fiber under test, and generates a stop pulse signal, so that the stop pulse signal does not change with the attenuation of the optical fiber under test, and timing is performed according to the start pulse signal, the clock signal and the stop pulse signal by a time-to-digital converter, and the optical fiber delay value is obtained, thereby improving the measurement accuracy of the optical fiber delay. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0035] Figure 1 It is a schematic diagram of the overall structure of the optical fiber delay measurement device of the present invention.

[0036] Explanation of symbols:

[0037] Pulse transmitter-1, optical transmitter-2, pulse signal shaping circuit-21, laser current driving circuit-22, laser component-23, automatic power control circuit-24, automatic temperature control circuit-25, optical receiver-3, photodetector-31, preamplifier-32, controllable gain amplifier-33, automatic gain control circuit-34, comparison amplifier-35, clock unit-4, time digital converter-5, control unit-6, optical fiber under test-7. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] The purpose of the present invention is to provide an optical fiber delay measurement device, wherein a start pulse signal is generated by a pulse transmitter, an optical transmitter adopts a dark pulse mode to modulate the start pulse signal, and transmits a dark pulse optical signal to the optical fiber under test, an optical receiver receives the optical pulse signal output by the optical fiber under test, and generates a stop pulse signal, so that the stop pulse signal does not change with the attenuation of the optical fiber under test, and timing is performed according to the start pulse signal, the clock signal and the stop pulse signal through a time-to-digital converter, and the optical fiber delay value is obtained, thereby improving the measurement accuracy of the optical fiber delay.

[0040] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0041] like Figure 1 As shown, the optical fiber delay measurement device of the present invention includes: a pulse transmitter 1, an optical transmitter 2, an optical receiver 3, a clock unit 4, a time-to-digital converter 5 and a control unit 6.

[0042] Wherein, the pulse transmitter 1 is used to generate a start pulse signal.

[0043] The optical transmitter 2 is connected to the pulse transmitter 1 and one end of the optical fiber 7 under test, and the optical transmitter 2 is used to transmit a dark pulse optical signal to the optical fiber 7 under test according to the pulse signal.

[0044] The optical receiver 3 is connected to the other end of the optical fiber 7 under test, and is used to receive the optical pulse signal output by the optical fiber 7 under test, and generate a stop pulse signal according to the optical pulse signal. Preferably, the bandwidth of the optical receiver 3 is greater than 50 MHz.

[0045] The clock unit 4 is used to generate a clock signal. In this embodiment, the clock unit 4 uses an ECOC-2522-10.000-3-HC chip. The ECOC-2522-10.000-3-HC chip provides a 10 MHz high-stability clock signal to the time-to-digital converter 5 .

[0046] The time digital converter 5 is connected to the pulse transmitter 1, the optical receiver 3 and the clock unit 4 respectively, and the time digital converter 5 is used to perform timing according to the start pulse signal, the clock signal and the stop pulse signal to obtain a time digital signal. Specifically, the time digital converter 5 is a time digital conversion circuit. In this embodiment, the time digital conversion circuit adopts the TDC7201 chip of TI company.

[0047] The control unit 6 is connected to the time digital converter 5, and the control unit 6 is used to determine the optical fiber delay value according to the time digital signal.

[0048] The present invention adopts a pulse measurement method to measure the optical fiber delay, and measures the flight time of the optical pulse signal in the measured optical fiber through a time digital conversion circuit, thereby measuring the optical fiber delay. Specifically, the time digital signal is stored in a result register in the time digital conversion circuit, and the result register also stores a clock frequency value. The calculation method for calculating the optical fiber delay value based on the time digital signal can adopt an existing known calculation method. It can be calculated based on the calculation formula provided by different time digital conversion circuit chips and the data stored in the result register in the time digital conversion circuit TDC.

[0049] Specifically, the optical transmitter 2 includes a pulse signal shaping circuit 21 , a laser current driving circuit 22 and a laser component 23 .

[0050] The pulse signal shaping circuit 21 is connected to the pulse transmitter 1 , and is used to shape the start pulse signal to obtain a shaped pulse signal.

[0051] The laser current driving circuit 22 is connected to the pulse signal shaping circuit 21 , and the laser current driving circuit 22 is used to generate a driving current according to the shaped pulse signal.

[0052] The laser component 23 is connected to the laser current driving circuit 22 and one end of the optical fiber 7 under test respectively. The laser component 23 is used to generate a dark pulse light signal according to the driving current and output it to the optical fiber 7 under test.

[0053] Furthermore, the laser assembly 23 includes a laser, a backlight detector and an automatic power control circuit 24 .

[0054] The laser is connected to the laser current driving circuit 22 and one end of the optical fiber 7 under test, respectively, and the laser is used to generate a dark pulse light signal according to the driving current and output it to the optical fiber 7 under test. Specifically, the laser is a semiconductor laser. In this embodiment, the semiconductor laser is a distributed feedback semiconductor laser DFB-LD.

[0055] Preferably, the wavelength of the semiconductor laser is in the window of 1310nm and 1550nm. The average power of the optical signal output by the semiconductor laser ranges from -10dBm to 15dBm, preferably 0dBm. The width of the optical pulse signal output by the semiconductor laser ranges from 10ns to 200ns, preferably 50ns. The optical pulse repetition frequency of the semiconductor laser ranges from 10kHz to 500Hz, preferably 1kHz. In the present embodiment, the wavelength of the semiconductor laser is 1550nm. The peak power of the output optical pulse signal peak is 0dBm. The width of the optical pulse signal is 50ns. The repetition frequency of the optical pulse is 1kHz.

[0056] The backlight detector is arranged on the laser, and is used to detect the optical power of the dark pulse optical signal generated by the laser.

[0057] The automatic power control circuit 24 is connected to the backlight detector and the laser current driving circuit 22 respectively, and is used to control the driving current output by the laser current driving circuit 22 according to the optical power. By detecting the average level of the backlight signal, automatic optical power control is performed to stabilize the average output optical power of the optical transmitter 2, thereby stabilizing the pulse amplitude of the dark pulse optical signal.

[0058] Furthermore, the optical transmitter 2 also includes a thermistor, an automatic temperature control circuit 25 and a semiconductor refrigerator.

[0059] The thermistor is arranged on the laser and is used to detect the temperature of the laser.

[0060] The automatic temperature control circuit 25 is connected to the thermistor and is used to generate a temperature control signal according to the temperature of the laser. In this embodiment, the automatic temperature control circuit 25 uses the MAX1978 chip of MAXIM.

[0061] The semiconductor refrigerator is arranged on the laser and connected to the automatic temperature control circuit 25. The semiconductor refrigerator is used for cooling or heating according to the temperature control signal.

[0062] Specifically, the modulation mode of the optical pulse signal is a dark pulse mode, that is, when no pulse appears, the optical signal power is high, and when a pulse appears, the optical signal power is low or zero.

[0063] In the optical transmitter, when there is no pulse signal at the input end, corresponding to the "0" signal, the pulse signal shaping circuit generates a "0" signal, causing the laser current driving circuit to generate current and drive the laser to emit light.

[0064] When a pulse signal appears at the input end, corresponding to the "1" signal, the pulse signal shaping circuit generates a "1" signal, causing the laser current drive circuit to not output current, the laser not to emit light, and the output optical power to be 0 or an extremely low optical power level, generating a "dark" pulse optical signal corresponding to the pulse signal.

[0065] Specifically, the optical receiver 3 includes a photodetector 31 , a preamplifier 32 , a controllable gain amplifier 33 , an automatic gain control circuit 34 and a comparison amplifier 35 .

[0066] The photoelectric detector 31 is connected to the other end of the optical fiber 7 under test, and the photoelectric detector 31 is used to detect the optical pulse signal output by the optical fiber 7 under test and convert the optical pulse signal into an electrical signal.

[0067] The preamplifier 32 is connected to the photodetector 31, and is used to amplify the electrical signal to obtain a first amplified electrical signal. In this embodiment, the preamplifier 32 is a transimpedance amplifier. The transimpedance amplifier uses the OPA858 chip of TI company, and the transimpedance is 20kΩ.

[0068] The controllable gain amplifier 33 is connected to the preamplifier 32, and is used to amplify the first amplified electrical signal to obtain a second amplified electrical signal. In this embodiment, the controllable gain amplifier 33 uses the LMH6502 chip of TI.

[0069] The automatic gain control circuit 34 is connected to the controllable gain amplifier 33 , and the automatic gain control circuit 34 is used to adjust the gain of the controllable gain amplifier 33 according to the second amplified electrical signal.

[0070] The comparison amplifier 35 is connected to the controllable gain amplifier 33 and the time-to-digital converter 5 respectively, and is used to compare the second amplified electrical signal with the threshold level, perform signal regeneration, and obtain a stop pulse signal. Specifically, the comparison amplifier 35 uses the TLV3501 chip of TI.

[0071] In the optical transmitter of the present invention, after the modulation is performed in a "dark pulse" mode, since the transmitted signal is a dark pulse optical signal of a low duty cycle type, the average level value of the dark pulse optical signal is approximately equal to the amplitude level value of the optical pulse. Automatic power control is adopted in the optical transmitter to keep the pulse amplitude in the output optical signal unchanged. The optical receiver obtains the amplitude level of the pulse signal by detecting the average level of the received optical pulse signal, and automatically controls the gain of the controllable gain amplifier by using the average level of the optical pulse signal, so that the pulse amplitude of the second amplified electrical signal output by the controllable gain amplifier is stable. Therefore, even if the comparison amplifier uses a fixed comparison threshold, the ratio of the pulse amplitude level of the second amplified electrical signal to the comparison threshold level can still remain almost unchanged. In the process of regenerating the pulse signal, the rising edge position of the regenerated pulse signal does not change with the change of the input optical pulse signal level, which greatly reduces the influence of the optical fiber attenuation change on the optical fiber delay measurement. When the optical fiber loss changes, it can also ensure that the optical fiber delay measurement accuracy is almost unaffected, thereby improving the accuracy of the optical fiber delay measurement, and the circuit structure is simple and the cost is low.

[0072] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An optical fiber delay measurement device, characterized in that: The optical fiber delay measurement device comprises: A pulse transmitter, used for generating a start pulse signal; An optical transmitter, connected to the pulse transmitter and one end of the optical fiber under test, and used to transmit a dark pulse optical signal to the optical fiber under test according to the start pulse signal; The optical transmitter comprises: A pulse signal shaping circuit, connected to the pulse transmitter, for shaping the start pulse signal to obtain a shaped pulse signal; A laser current driving circuit, connected to the pulse signal shaping circuit, for generating a driving current according to the shaped pulse signal; A laser assembly, connected to the laser current driving circuit and one end of the optical fiber under test, respectively, for generating a dark pulse light signal according to the driving current and outputting it to the optical fiber under test; The laser assembly comprises: A laser is connected to the laser current driving circuit and one end of the optical fiber under test, respectively, and is used to generate a dark pulse light signal according to the driving current and output it to the optical fiber under test; the laser is a semiconductor laser; In the optical transmitter, when there is no pulse signal at the input end, corresponding to the "0" signal, the pulse signal shaping circuit generates a "0" signal, causing the laser current driving circuit to generate current and drive the laser to emit light; when there is a pulse signal at the input end, corresponding to the "1" signal, the pulse signal shaping circuit generates a "1" signal, causing the laser current driving circuit to not output current, the laser does not emit light, and the output optical power is 0 or a very low optical power level, generating a "dark" pulse optical signal corresponding to the pulse signal; A back-light detector, arranged on the laser, for detecting the optical power of the dark pulse optical signal generated by the laser; An automatic power control circuit is connected to the backlight detector and the laser current driving circuit respectively, and is used to control the driving current output by the laser current driving circuit according to the optical power; by detecting the average level of the backlight signal, automatic optical power control is performed to stabilize the average output optical power of the optical transmitter, thereby stabilizing the pulse amplitude of the dark pulse optical signal; an optical receiver connected to the other end of the optical fiber under test, and configured to receive the optical pulse signal output by the optical fiber under test, and generate a stop pulse signal according to the optical pulse signal; A clock unit, used for generating a clock signal; A time digital converter, connected to the pulse transmitter, the optical receiver and the clock unit respectively, for timing according to the start pulse signal, the clock signal and the stop pulse signal to obtain a time digital signal; A control unit is connected to the time digital converter and is used to determine the optical fiber delay value according to the time digital signal.

2. The optical fiber delay measurement device according to claim 1, characterized in that: The optical transmitter also includes: a thermistor, disposed on the laser and used to detect the temperature of the laser; An automatic temperature control circuit, connected to the thermistor, for generating a temperature control signal according to the temperature of the laser; The semiconductor refrigerator is arranged on the laser and connected to the automatic temperature control circuit, and is used for cooling or heating according to the temperature control signal.

3. The optical fiber delay measurement device according to claim 1, characterized in that: The semiconductor laser component is a distributed feedback semiconductor laser.

4. The optical fiber delay measurement device according to claim 1, characterized in that: The optical receiver comprises: A photoelectric detector connected to the other end of the optical fiber under test, used to detect the optical pulse signal output by the optical fiber under test and convert the optical pulse signal into an electrical signal; a preamplifier, connected to the photodetector, and used to amplify the electrical signal to obtain a first amplified electrical signal; a controllable gain amplifier, connected to the preamplifier, and configured to amplify the first amplified electrical signal to obtain a second amplified electrical signal; an automatic gain control circuit, connected to the controllable gain amplifier, and configured to adjust the gain of the controllable gain amplifier according to the second amplified electrical signal; The comparison amplifier is connected to the controllable gain amplifier and the time-to-digital converter respectively, and is used to compare the second amplified electrical signal with the threshold level, perform signal regeneration, and obtain a stop pulse signal.

5. The optical fiber delay measurement device according to claim 4, characterized in that: The preamplifier is a transimpedance amplifier.

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