JPH069356Y2 - Optical pulse tester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention supplies a light pulse to a fiber to be measured, detects backscattered light and Fresnel reflected light reflected from the fiber to be measured, and determines a predetermined value. By performing the signal processing of
The present invention relates to an optical pulse tester that measures the optical loss of a measured fiber and the position of a fault point.

[Prior Art] An optical pulse is supplied to a measured fiber, and the backscattered light and Fresnel reflected light reflected from the measured fiber are detected and a predetermined signal processing is performed to cause optical loss or damage of the measured fiber. An optical pulse tester is known as a device for measuring a point position.

FIG. 3 shows a schematic structure of such an optical pulse tester.

The optical pulse tester is roughly configured to include a light emitting section 1, a branch section 2, a detecting section 3, a processing section 4, and a display section 5.
When a light pulse of a predetermined level is supplied to the measured fiber 6, the backscattered light and Fresnel reflected light reflected from the measured fiber 6 are branched by the branching section 2 and detected by the detecting section 3. The detection signal is level-amplified in the processing unit 4, A / D-converted, further sampled at a predetermined sampling period, and then waveform-processed for each data and displayed on the display unit 5.

[Problems to be Solved by the Invention] By the way, in the above-described optical pulse tester, the backscattered light level from the measured fiber 6 with respect to the incident level of the optical pulse is detected most effectively by the detection unit 3. The light receiving system is designed. Further, the incident level of the light pulse is uniquely fixed and set. Therefore, when Fresnel reflected light having a high level of about 30 to 50 dB with respect to the level of the backscattered light is incident on the detection unit 3, the light receiving system of the detection unit 3 is saturated and the waveform cannot be observed for a predetermined time.
There is a problem that a so-called dead zone occurs and even if another Fresnel reflected light enters the detection unit 3 during this dead zone, the Fresnel reflected light cannot be detected.

Therefore, the present invention has been made in view of the above-mentioned problems, and the purpose thereof is to automatically variably control the level of the optical pulse supplied to the fiber to be measured to an optimum state, which has been conventionally caused. An optical pulse that can accurately and reliably detect Fresnel reflected light from a fault point buried in the dead zone by making the dead zone extremely short and increase the resolution to measure the fault point position of the measured fiber. To provide a tester.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the optical pulse tester according to the present invention comprises a light emitting section 7 capable of supplying the measured fiber 6 with varying levels of the optical pulse, and the measured fiber. A detection unit 9 that detects the peak value of the output Fresnel reflected light, a comparison unit 10 that compares the peak value with a predetermined level value L that is set below the saturation level of the detection unit in advance, and the comparison unit. A processing unit 11 for calculating and outputting an optimum value for controlling the level of the light pulse of the light emitting unit so that the peak value becomes the predetermined level value L based on the comparison result of And a level control unit 13 for controlling the output level of the light pulse emitted by the light emitting unit based on the optimum value.

[Operation] When a light pulse of a predetermined level is supplied from the light emitting section 7 to the fiber 6 to be measured, the peak value of the Fresnel reflected light output from the fiber 6 to be measured is supplied from the detection section 9 along with the supply of this light pulse To detect. This detection signal is compared with the level value L set beforehand based on the saturation level Lh of the detection unit 9 in the comparison unit 10, and the peak value is previously detected in the detection unit in the processing unit 11 based on the comparison result. The optimum value for controlling the level of the light pulse of the light emitting unit 7 is calculated and calculated so that the level value L is set to be equal to or lower than the saturation level of 9. Then, the level control unit 13 controls the output level of the light pulse emitted by the light emitting unit 7 based on the optimum value of the calculation result.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of an optical pulse tester according to the present invention.

The optical pulse tester according to this embodiment includes a light emitting unit 7, a branching unit 8, a detecting unit 9, a comparing unit 10, a processing unit 11, a display unit 12,
The level control unit 13 and the detection position setting unit 14 are provided. When an optical pulse of a predetermined level is supplied to the measured fiber 6, the optical pulse is output from the measured fiber 6 along with the supply of the optical pulse. The peak value of the Fresnel reflected light is detected, and the detected signal is compared with a predetermined level value L which is a value equal to or lower than the saturation level of the detection unit 9 which is determined in advance. By increasing or decreasing the level of, the optimum value for controlling the level of the light pulse of the light emitting section 7 is calculated and calculated so that the peak value becomes the level value L, and the light emitting section emits light based on this optimum value. The output level of the optical pulse is controlled variably.

The light emitting section 7 emits an optical pulse of a predetermined level to the measured fiber 6 via the branch section 8 based on a signal output from the level control section 13 via the processing section 11 described later.

The branching unit 8 includes, for example, an optical directional coupler, and the light emitting unit 7
While guiding the optical pulse from the to the measured fiber 6 side,
The backscattered light and the Fresnel reflected light output from the measured fiber 6 in accordance with the supply of the optical pulse are branched to the detector 9 side.

The light receiving system provided inside the detection unit 9 detects the backscattered light and Fresnel reflected light output from the measured fiber 6 via the branching unit 8. This detection signal is processed by the processing unit 11
Output to the same as the above-mentioned [Conventional Technology], that is, after level amplification and A / D conversion, sampling is performed for each data and waveform processing, and the result is displayed. The waveform is displayed on the screen. The detector 9 also includes a peak detector 16 for detecting the peak value of the reflected light from the fiber 6 to be measured, which is detected by the light receiving system.
It outputs to 0.

The comparison unit 10 compares the detection signal (peak value) supplied from the peak detection unit 16 with the level value L set in advance based on the saturation level of the light receiving system of the detection unit 9, and the result is processed by the processing unit 11 Is output to.

The set level value L is set to a value lower than the saturation level Lh of the detection unit 9 by about 2 to 3 dB as shown in FIG. 2 in view of the relationship between the S / N ratio and the dynamic range.

The processing unit 11 processes the signal output from the detection unit 9 and causes the light emitting unit 7 to measure the measured value so that the peak value, which is the signal output from the peak detection unit 16, becomes a predetermined level value L. The optimum value for controlling the level of the optical pulse supplied to the fiber 6 is calculated and calculated.

The level control unit 13 sets the output level of the light emitting unit 7 to the optimum level based on the optimum value calculated by the processing unit 11.
That is, the light receiving system of the detector 9 that detects the Fresnel reflected light from the fiber 6 to be measured is automatically variably controlled to a level value L that does not saturate. Further, the level control section 13 is provided with a switching means, and the output level of the light emitting section 7 can be controlled automatically and manually based on the switching operation of the switching means. In this case, manual control is performed by an operator's key operation.

Therefore, when the output level of the optical pulse output from the light emitting section 7 is variably controlled as described above, the measured fiber 6
The output level of the Fresnel reflected light output from the detector 9 is
Since it is suppressed below the saturation level Lh, the dead zone caused by the saturation of the light receiving system of the conventional detector can be eliminated, and the dead zone reflects the Fresnel reflection from the measured fiber in the section where the waveform cannot be observed. The light can be detected accurately and reliably, and the position of the faulty point of the measured fiber can be measured with high accuracy.

The detection position setting unit 14 sets the measurement position of the fiber 6 to be measured during or during measurement, and the display screen 17 is operated based on the operation of an external key switch (not shown).
This is performed by moving the upper marker 18 to a desired position, and at the same time as this operation, the output level of the light emitting unit 7 is variably controlled based on the level of the position of the marker 18.

Here, FIG. 2 shows the waveforms of the backscattered light and Fresnel reflected light of the measured fiber displayed on the display screen 17 of the display unit 12, and the portion shown by the broken line in the drawing shows the output waveform in the dead zone. Is shown.

Therefore, by moving the marker 18 on the screen 17 by a key operation while visually observing the display screen 17 of the display unit 12, the level control of the light pulse output from the light emitting unit 7 is performed with reference to the level of the position of the marker 18. Since the measurement can be performed, it is possible to measure the optical loss and the fault point in a part of the measured fiber 6 with high accuracy.

Next, the operation of the optical pulse tester configured as described above will be described.

First, an external key switch is operated to move the marker 18 on the display screen 17 to set the measurement position of the fiber 6 to be measured. In this state, the light emitting portion 7 is
When the optical pulse is further supplied, the waveforms of the backscattered light and Fresnel reflected light are displayed on the display unit 12 from the measured fiber 6. Then, the peak value of the Fresnel reflected light detected by the peak detector 16 is detected. Next, this peak value is compared with the saturation level Lh of the detection unit 9 in advance in the comparison unit 10.
The optimum value for controlling the level of the light pulse of the light emitting unit 7 by the processing unit 11 so that the peak value becomes the level value L based on the comparison result. A value, that is, a value at which the detected output level of the reflected light does not reach the saturation level Lh is calculated and calculated. Then, the level control unit 13 variably controls the level of the optical pulse output from the light emitting unit 7 according to the optimum value calculated by the processing unit 11.

Therefore, the level of the optical pulse output from the light emitting section 7 is variably controlled by the signal according to the level of the reflected light output from the level control section 13, so that the reflected light from the measured fiber 6 can be detected reliably and accurately. Then, various measurements such as light loss and obstacle points can be performed.

[Effect of Device] As described above, according to the optical pulse tester of the present invention,
According to the level of the Fresnel reflected light from the fiber under measurement detected by the detection section, the level of the light pulse output from the light emitting section can be variably controlled automatically to the optimum state. Therefore, the dead zone due to the saturation of the light receiving system, which has occurred in the past, can be extremely shortened, and Fresnel reflected light from the fault point, which was buried in this dead zone, can be detected accurately and reliably. There is an effect that the point of failure of the fiber can be measured.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of an optical pulse tester according to the present invention, and FIG. 2 is a waveform diagram of backscattered light and Fresnel reflected light displayed on the display section of the optical pulse tester.
FIG. 3 is a diagram for explaining the schematic structure of the optical pulse tester. 6 ... Fiber to be measured, 7 ... Light emitting part, 9 ... Detection part, 10 ...
Comparing unit, 11 ... Processing unit, 13 ... Level control unit.

Claims (1)

[Scope of utility model registration request] 1. A light emitting section (7) capable of varying and supplying an optical pulse level to a measured fiber (6), and a detection section (9) for detecting a peak value of Fresnel reflected light output from the measured fiber. ), A comparison unit (10) that compares the peak value with a predetermined level value L that is set to a saturation level of the detection unit or less in advance, and based on the comparison result of the comparison unit,
A processing unit (11) that calculates and outputs an optimum value for controlling the level of the light pulse of the light emitting unit so that the peak value becomes the predetermined level value L; An optical pulse tester, further comprising: a level control unit (13) for controlling an output level of an optical pulse emitted by the light emitting unit.