JP5445004B2 - Optical pulse tester - Google Patents

Description

  The present invention includes a pulse generation unit that emits an optical pulse toward an optical fiber, a photon detection unit that detects photons contained in Rayleigh backscattered light based on the optical pulse, and counts photons detected by the photon detection unit. The present invention relates to an optical pulse tester including a photon counting unit.

  As an apparatus for measuring the characteristics of an optical fiber, an OTDR (Optical Time Domain Reflectometer) using a photon counting method is known. In this apparatus, the characteristics of an optical fiber are measured by irradiating an optical fiber with a laser pulse and detecting photons contained in the Rayleigh Backscatter Signal (RBS) with an avalanche photodiode. The avalanche photodiode operates in Geiger mode when a gate signal is applied, and detects photons only when the gate signal is applied. The relationship between the fiber distance and the photon count is obtained by changing the timing of applying the gate signal little by little and counting the photons detected at that time.

US Patent Publication No. 2008/0231842

  In the above apparatus, a gate signal is applied once each time a laser pulse is irradiated. For this reason, in order to measure a long optical fiber with a sufficient dynamic range, it is necessary to irradiate a laser pulse many times, and a long time is required for the measurement. However, the conventional apparatus has a disadvantage that the user does not know when the measurement is finished and has to wait until the measurement is finished.

  The objective of this invention is providing the optical pulse tester which can notify a user beforehand about the time concerning a measurement.

The optical pulse tester of the present invention is detected by a pulse generator that emits an optical pulse toward an optical fiber, a photon detector that detects photons contained in Rayleigh backscattered light based on the optical pulse, and a photon detector A photon counting unit that counts the photons detected, and the photon counting unit counts while changing a timing of applying a gate signal that enables detection in the photon detecting unit to the photon detecting unit. In an optical pulse tester that obtains the relationship between the fiber distance and the photon count number, the measurement is based on the dynamic range of the measurement based on the count number, the measurement distance range of the optical fiber, and the gate width of the gate signal. Measurement time calculation means for calculating the time required for the measurement, and the measurement time calculation means A display means for displaying the time, the dynamic range of measurement based on the count, the measurement distance range of the optical fiber, or a measurement condition setting means for receiving settings of the gate width of the gate signal, the measurement condition setting Measurement start means for receiving an instruction to start measurement according to the setting state received by the means, and the measurement time calculation means calculates the time corresponding to the latest setting state received by the measurement condition setting means and, wherein the measurement condition setting means, wherein until receiving an instruction to start the measurement by the measurement starting means, characterized in Rukoto accepts change of the setting state.
According to this optical pulse tester, the time required for measurement is calculated and displayed based on the dynamic range of measurement based on the number of counts, the measurement distance range of the optical fiber, and the gate width of the gate signal. Such time can be notified to the user in advance.

  Control means for controlling the time displayed by the display means to count down during measurement may be provided.

  According to the optical pulse tester of the present invention, the time required for measurement is calculated and displayed based on the dynamic range of measurement based on the number of counts, the measurement distance range of the optical fiber, and the gate width of the gate signal. The user can be notified in advance of the time required for measurement.

The block diagram which shows the structure of the optical pulse tester of one Embodiment. The figure which shows the display screen of a display part.

  Hereinafter, an embodiment of an optical pulse tester according to the present invention will be described.

  FIG. 1 is a block diagram illustrating a configuration of the optical pulse tester according to the present embodiment, and FIG. 2 is a diagram illustrating a display screen of a display unit.

  As shown in FIG. 1, an optical pulse tester 1 according to this embodiment includes a pulse generator 11 that emits a laser pulse toward an optical fiber 2 that is a device under test, and an avalanche photodiode. The photon detection unit 12 that detects photons included in the Rayleigh backscattered light returning from 2, the photon count unit 13 that counts photons detected by the photon detection unit 12, and the measurement result based on the count number in the photon count unit 13 A display unit 14 for displaying, a dynamic range / parameter storage unit 15 for storing a value of a dynamic range of measurement, a measurement distance parameter storage unit 16 for storing a value of each section distance from a measurement start position to a measurement end position, A gate that stores the time width (gate width) value of the gate signal applied to the photon detector 12 A parameter storage unit 17, a measurement time calculation unit 18 that calculates the time required for measurement, a measurement condition setting unit 19 that accepts selection of measurement conditions, a pulse generation unit 11, a photon detection unit 12, a photon count unit 13, and a display Unit 14, a dynamic range / parameter storage unit 15, a measurement distance parameter storage unit 16, a gate width parameter storage unit 17, a measurement time calculation unit 18, and a control unit 20 for controlling the measurement condition setting unit 19.

  At the time of measurement, the value of the dynamic range of measurement given from the dynamic range / parameter storage unit 15, the measurement distance parameter storage unit 16 and the gate width parameter storage unit 17, the value of each section distance from the measurement start position to the measurement end position, and Based on the value of the time width (gate width) of the gate signal applied to the photon detector 12, the laser pulse emission timing in the pulse generator 11 and the photon detection timing in the photon detector 12 are controlled.

  The avalanche photodiode constituting the photon detector 12 operates in the Geiger mode when a gate signal is applied, and detects photons only when the gate signal is applied. The photon count unit 13 counts the photons detected at that time while gradually changing the timing of applying the gate signal (elapsed time from the laser pulse emission), so that the relationship between the fiber distance and the photon count number can be obtained. Can be obtained. The gate signal is applied to the photon detection unit 12 once every time a pulse of the laser is emitted from the pulse generation unit 11.

  As shown in FIG. 2, a graph indicating the relationship between the fiber distance and the photon count number is displayed as a measurement result in the area 14 a on the screen of the display unit 14 according to the count number in the photon count unit 13. . In this graph, the distance (measurement position) of the optical fiber 2 is shown on the horizontal axis, and the intensity of Rayleigh backscattered light based on the photon count is shown on the vertical axis. The distance of the optical fiber 2 shown on the horizontal axis corresponds to the elapsed time from the laser pulse emission by the pulse generator 11 to the time of photon detection (timing for applying a gate signal) in the photon detector 12.

  Prior to measurement, the measurement time calculation unit 18 ends the measurement from the measurement dynamic range value and the measurement start position given from the dynamic range / parameter storage unit 15, measurement distance parameter storage unit 16 and gate width parameter storage unit 17, respectively. The time required for measurement is calculated based on the value of each section distance to the position and the time width (gate width) of the gate signal applied to the photon detector 12.

  For example, when measuring the entire 20 km optical fiber, the measurement time is obtained by the following calculation.

In order to suppress the secondary reflection of the fiber end face, it is necessary to set the repetition period of the laser pulse to 0.4 ms or more corresponding to twice or more of 20 km. If the width of the gate signal is 40 ns, a 20 km long fiber is divided into 10 ⁴ sections. When the dynamic range of the measuring and 20 dB (5 log ₁₀ displays), it is necessary to gate the number of applications of 10 ⁴ times per one section. Therefore, the measurement time is calculated by the number of times of gate application (10 ⁴ ) × laser cycle (0.4 ms) × number of sections (10 ⁴ ), and is 4 × 10 ⁴ seconds. That is, the measurement time exceeds 11 hours.

  As shown in FIG. 2, the calculation result in the measurement time calculation unit 18 is displayed in an area 14 b on the screen of the display unit 14. In this example, it is displayed that the time required for the measurement is 11 hours 6 minutes 40 seconds. Although it takes a long time to measure a long optical fiber with a sufficient dynamic range, according to the present embodiment, the measurement time is displayed in advance, so that the user can know the measurement end time and the like. In the calculation in the measurement time calculation unit 18, more precise calculation may be executed in consideration of the margin of the measurement distance, the time required for controlling the apparatus, and the like.

  The time displayed in the area 14 b on the screen of the display unit 14 can be counted down with the start of measurement according to the control by the control unit 20. As a result, the remaining time until the end of the measurement is clearly indicated, so that the user can always know the end time of the measurement at the time of measurement.

  The measurement condition setting unit 19 includes a measurement dynamic range value stored in the dynamic range / parameter storage unit 15, measurement distance parameter storage unit 16, and gate width parameter storage unit 17, each section from the measurement start position to the measurement end position. It functions as an interface for accepting a user operation for setting the distance value and the time width (gate width) value of the gate signal applied to the photon detector 12. These values that define the measurement conditions can be changed according to the user's operation via the measurement condition setting unit 19 and are reflected in the calculation result in the measurement time calculation unit 18. For this reason, the user can select measurement conditions while referring to the time required for measurement. If the measurement is started after selecting the measurement conditions, the measurement is executed according to the set measurement conditions. Also in this case, the time displayed in the area 14b on the screen of the display unit 14 can be counted down with the start of measurement.

  The measurement condition setting unit 19 can be configured using buttons and switches provided in the optical pulse tester 1. Further, an interface function may be provided in a computer or the like outside the optical pulse tester 1 so that measurement conditions can be set via a wired or wireless communication function.

  The measurement condition setting unit 19 may be omitted and the measurement condition may be fixed.

  As described above, according to the optical pulse tester of the present invention, the time required for the measurement is calculated based on the dynamic range of the measurement based on the count number, the measurement distance range of the optical fiber, and the gate width of the gate signal. In this case, the user can be notified in advance of the time required for measurement.

  The scope of application of the present invention is not limited to the above embodiment. The present invention includes a pulse generation unit that emits an optical pulse toward an optical fiber, a photon detection unit that detects photons contained in Rayleigh backscattered light based on the optical pulse, and counts photons detected by the photon detection unit. The present invention can be widely applied to an optical pulse tester including a photon counting unit.

DESCRIPTION OF SYMBOLS 11 Pulse generation part 12 Photon detection part 13 Photon count part 14 Display part (display means)
18 Measurement time calculator (Measurement time calculator)
19 Measurement condition setting section (Measurement condition setting means)
20 Control unit (control means)

Claims (2)

A pulse generation unit that emits an optical pulse toward an optical fiber, a photon detection unit that detects photons contained in Rayleigh backscattered light based on the optical pulse, and a photon count unit that counts photons detected by the photon detection unit And the distance of the optical fiber and the number of photons counted by performing the counting in the photon counting unit while changing the timing of applying a gate signal to enable the detection in the photon detecting unit to the photon detecting unit. In the optical pulse tester for obtaining the relationship of
A measurement time calculation means for calculating a time required for measurement based on a dynamic range of measurement based on the count number, a measurement distance range of the optical fiber, and a gate width of the gate signal;
Display means for displaying the time calculated by the measurement time calculating means;
A measurement condition setting means for receiving a setting of a dynamic range of measurement based on the count number, a measurement distance range of the optical fiber, or a gate width of the gate signal;
Measurement start means for receiving an instruction to start measurement according to the setting state received by the measurement condition setting means;
With
The measurement time calculation means calculates the time corresponding to the latest setting state received by the measurement condition setting means,
The measurement condition setting means, OTDR, wherein Rukoto accepts change of the setting state until receiving an instruction to start the measurement by said measurement start means. 2. The optical pulse tester according to claim 1 , further comprising control means for controlling the time displayed by the display means to count down during measurement .

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