JPH0610277Y2 - Optical fiber cable test equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial Application Field" The present invention relates to an optical fiber cable testing device for testing the quality of each optical fiber mounted on a multi-core optical fiber cable.

"Prior Art" Optical fiber cable manufacturers or contractors who install optical fiber cables test the quality of the completed optical fiber cable or the optical fiber cable to be installed. Since an optical fiber cable is generally multicore, it is convenient to connect the end of each optical fiber to a test device at a time and to test the quality of all the optical fibers in the connected state.

FIG. 4 shows the overall configuration of the optical fiber cable testing device. The optical fiber cable testing device is roughly divided into a light source device 100 and a light receiving device 200.

The light source device 100 includes a plurality of light sources 101A, 101B, 101C ... 101N and exciters 102A, 102B, 102C ... Exciting the light sources 101A to 101N.
It is composed of 102N and.

A light emitting element such as a light emitting diode or a laser diode is used as each of the light sources 101A to 101N.
A to 102N have a function of lighting the light sources 101A to 101N by both DC lighting and intermittent lighting.

The light receiving device 200 includes a plurality of light receivers 201A, 201B, 201C ... 201N,
A current-voltage conversion circuit 202 for converting the photoelectric conversion current photoelectrically converted by the light receivers 201A to 201N into current-voltage (see FIG. 5).
And an AC component A generated by intermittent light from the received light signal which is converted into a voltage signal by the voltage-current conversion circuit 202 and is extracted.
An AC amplifier 203 that extracts C (see FIG. 6) by a capacitor 203A and amplifies it, a filter 204 that waves the AC component AC amplified by this AC amplifier 203, and an AC component AC that is waved by the filter 204 are synchronously detected, for example. , An AC / DC converter 20 for converting to a DC voltage proportional to the level of the AC component AC
5 and an indicator 206 for displaying the value of the DC voltage converted by the AC / DC converter 205.

Each end of each of the optical fibers 301A to 301N of the optical fiber cable 300 has a light source 101A to 101N and an optical receiver by an optical connector or the like.
Coupled to 201A-201N.

The optical fiber to be tested has a specified frequency, for example 27
Giving intermittent light that is intermittent at 0 Hz, and receiving this intermittent light
Photoelectric conversion is performed with the light receivers 201A, 201B, 201C ... 201N provided in 00,
The photoelectrically converted intermittent current is converted into a voltage signal by the current-voltage conversion circuit 202, this voltage signal is amplified by the AC amplifier 203 and converted into direct current by the AC / DC conversion circuit 205, and this direct current is given to the indicator 206, which is intermittent. The quality of the optical fiber is judged by displaying the amount of light.

Therefore, the vibrators 102A, 102B, 102C, ...
101A to 101N are intermittently driven to test each optical fiber 301A, 301B, 301C ... 301N of the optical fiber cable 300 one by one.

By the way, a light source such as a light emitting diode or a laser diode has a characteristic that the light emission intensity is unstable at the beginning of lighting. Therefore, when testing multiple optical fibers, each light source 101A, 101B, 101C ...
101A to 101N are lit by direct current to constantly excite the light source,
Only the light sources in the order to be tested are lit intermittently.

"Problems to be solved by the device" Since direct current light is applied to the optical fiber in the non-test state from the light source turned on by direct current, the light receiving device 200 obtains the direct current component DC by intermittent light as shown in FIG. The AC component AC is superposed.

The DC component DC shown in FIG. 6 has a total number of optical fibers of 5
If it is a book, it becomes the value of the sum of four direct current lights,
The AC component AC appears as an amplitude caused by the interruption of the light in one optical fiber.

If the optical fiber being tested by the application of intermittent light is normal, the amplitude of the AC component AC has an amplitude corresponding to the intermittent amount of light from one optical fiber, so the current-voltage conversion circuit 20
2 can perform current-voltage conversion within the normal linear range of the input / output characteristics, and can send the AC component AC to the AC amplifier 203.

However, in the case of an optical fiber that has a defect on the way and the amount of transmitted light is greatly attenuated, the AC component AC
Will be reduced in amplitude. Therefore, the AC amplifier 20
It is necessary to increase the gain of the current-voltage conversion circuit 202 in order to give the AC component AC having a prescribed amplitude to 3, but if the gain of the current-voltage conversion circuit 202 is increased even slightly, the current-voltage conversion circuit 202 will generate the DC component DC. This causes an inconvenience of immediate saturation.

When the current-voltage conversion circuit 202 becomes saturated, the amplitude of the AC component output to the output side becomes smaller and smaller, which makes it impossible to measure the attenuation amount of a defective optical fiber.

"Means for Solving Problems" In this invention, in the optical fiber cable testing device,
Corresponding to a plurality of optical fibers that emit intermittent light from a book and direct current light of approximately the same level from other things, a plurality of light receivers that respectively receive the emitted light are provided. A direct current removing unit is provided on the input side of one current-voltage converting circuit for commonly converting the output photoelectric conversion current into a voltage signal, and the direct current removing unit removes the direct current component output from the light receiving unit. It is a thing.

According to the configuration of the present invention, for example, even if each LED light source is turned on in a non-test state, the light source is turned on by direct current, the light source is always excited, and only the LED light source of the order to be tested is turned on intermittently. Since a stable constant level of intermittent light can be supplied from the beginning of the above, and the DC component is removed from the photoelectric conversion current provided to the current-voltage conversion circuit, the current-voltage conversion circuit will not be saturated by the DC component.

Therefore, even if there is a defective optical fiber in the optical fiber cable that bundles multiple optical fibers, the current-voltage conversion circuit will not be saturated when testing the optical fiber. The fiber can also measure its attenuation accurately.

"Embodiment" FIG. 1 shows an embodiment of the present invention. In FIG. 1, parts corresponding to those in FIG. 5 are designated by the same reference numerals. In this embodiment, the case where the direct current removing means 207 is constituted by an integrating circuit is shown.

That is, the DC removing means 2 is provided on the output side of the current-voltage conversion circuit 202.
The input terminal of the integrator constituting 07 is connected, and the output terminal of the integrator is connected to the input side of the current-voltage conversion circuit 202.

With such a configuration, the integrator that constitutes the DC removing means 207 integrates the DC component DC that appears on the output side of the current-voltage conversion circuit 202 and negatively feeds back the integrated output to the input side of the current-voltage conversion circuit 202. .

As a result, the DC component DC is removed from the photoelectric conversion current input to the current-voltage conversion circuit 202, and as shown in FIG. 2, only the AC component AC is output to the output side of the current-voltage conversion circuit 202.

Therefore, since the DC component DC given from the light receivers 201A to 201N is not input to the current-voltage conversion circuit 202, the current-voltage conversion circuit 202 is not saturated by the DC component DC.
Therefore, since one optical fiber in the optical fiber cable has a defect, the amount of light attenuation is large, and therefore the AC component A
Since the amplitude of C is small, the current-voltage converting circuit 202 is not saturated even if the gain of the current-voltage converting circuit 202 is increased, and the optical fiber can be correctly tested under any conditions.

FIG. 3 shows another embodiment of the present invention. In this embodiment, the case where the DC removing means 207 is constituted by the DA converter 207A and the voltage-current converter 207B is shown.

That is, a digital signal having a value corresponding to the DC component DC is given to the DA converter 207A, this digital signal is converted into an analog voltage, and this analog voltage is converted into a voltage-current converter.
The current signal is converted by 207B, this current signal is given to the input side of the current-voltage conversion circuit 202, the DC component DC flowing into the current-voltage conversion circuit 202 is sucked into this voltage-current converter 207B, and the DC component DC is removed. The configuration is shown below.

The digital signal supplied to the DA converter 207A is structured, for example, by a manually set type digital switch (not shown), or an AD converter (not shown) is provided on the input side of the DA converter 207A. The output voltage of the current-voltage conversion circuit 202 is applied to the input side of the AD converter,
This output voltage is AD converted, and this digital signal is DA converted.
It can also be configured to give a closed loop to the converter 207A.

[Advantage of the Invention] As described above, according to the present invention, a plurality of optical fibers give almost the same level of DC light, and one optical fiber among them gives a stable constant level of intermittent light from the beginning of lighting. Since the DC removing means 207 is provided on the input side of the current-voltage conversion circuit 202 that converts the photoelectric conversion currents of the plurality of light receivers to the voltage, the amplitude of the AC component AC input from the light receivers 201A to 201N is small. Even if the gain of the current-voltage conversion circuit 202 is increased, the current-voltage conversion circuit 20
The DC current input to 2 can be removed by the DC removing means 207.

Therefore, since the current-voltage conversion circuit 202 is not saturated by the DC component DC, it is possible to perform a stable test even with an optical fiber that cannot transmit intermittent light at a sufficient level due to a defect, and a reliable optical fiber cable A test device can be provided.

In the above description, a plurality of light receivers 201A to 201A are provided on the light receiving side.
Although the case where N is provided has been described, one light receiver may be configured to receive light of a plurality of optical fibers.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining an embodiment of the present invention, FIG. 2 is a waveform diagram for explaining the operation of the present invention,
FIG. 3 is a block diagram showing another embodiment of the present invention, and FIG.
FIG. 5 is a block diagram for explaining the structure of the optical fiber cable testing device, FIG. 5 is a block diagram for explaining the conventional technique, and FIG. 6 is a waveform diagram for explaining the drawbacks of the conventional technique. . 100: light source device, 200: light receiving device, 201A to 201N: light receiving device,
202: voltage-current conversion circuit, 203: AC amplifier, 204: filter, 205: AC / DC converter, 206: indicator, 300: optical fiber cable, 301A to 301N: optical fiber.

Claims (1)

[Scope of utility model registration request] 1. A. A plurality of optical fibers that emit intermittent light from one optical fiber and emit a plurality of optical fibers that emit approximately the same level of direct current light from the other optical fibers, respectively, and each receive the emitted light; One current-voltage conversion circuit that commonly amplifies the photoelectric conversion current obtained from these light receivers; An indicator for detecting the AC component of the intermittent light component obtained on the output side of the current-voltage conversion circuit and displaying the magnitude of the AC component; An optical fiber cable test apparatus comprising: a direct current removing unit provided on the input side of the current-voltage converting circuit for removing a direct current component contained in the photoelectric conversion current.