JP2745319B2 - Optical output measuring device for multi-core optical fiber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial applications]

The present invention relates to a multi-core optical fiber optical output measuring device that measures light emitted from each core of a multi-core optical fiber.

[Prior art]

Conventionally, light is sequentially incident on the core wire of each channel of a multi-core optical fiber using an instantly stable multi-channel light source,
The light emitted from the other end is guided to a common photoelectric conversion element (light receiving element) regardless of the core of any channel, and each channel is determined based on a known order of light incidence on the core of each channel. An optical output measuring device of a multi-core optical fiber which measures the optical output every time is known (JP-A-62-91).
No. 832). In this case, on the light receiving side, light sequentially emitted from the core wire of each channel is incident on the same light receiving element, and an electric signal corresponding to each channel is sequentially output from this one light receiving element, and A / A It is sent to a measurement circuit such as a D converter, and a measured value output corresponding to the level of the electric signal is obtained.In general, the signal level is adjusted so that the above electric signal level falls within the measurement range of the measurement circuit. A range-switching amplifier is inserted before the measurement circuit. This range switching amplifier automatically switches the gain stepwise in relatively large units in accordance with the level of the input signal, so that the range is switched every time a signal of each channel is input. Has become.

[Problems to be solved by the invention]

However, conventionally, the range switching amplifier performs range switching by gradually decreasing the gain in order from the maximum gain, and repeats this uniformly for each channel signal. In this case, after decreasing the gain by one step,
Without waiting for the output signal to reach a steady state, it is not possible to determine whether it is necessary to further reduce the gain by one step or to use that gain. However, when the gain was changed, the output signal was then set to 100 msec until the output signal became steady.
Since it takes a time of ~ / 200 msec, it takes a considerable time to determine the gain in each channel. In practice, the time required for sampling the level of the received light signal and obtaining the output of the measured value is relatively short, and the time required for range switching in the range switching circuit is very long compared to this time. The ratio of the time for switching the range to the measurement time is large. In particular, when a photoelectric conversion element having a large dynamic range is used, the number of gain switching stages increases, so that the time required for range switching becomes even longer. SUMMARY OF THE INVENTION It is an object of the present invention to provide an optical output measuring device for a multi-core optical fiber, which can shorten the time for range switching and shorten the measuring time as a whole.

[Means for Solving the Problems]

In order to achieve the above object, according to the present invention, light is sequentially incident on each core from one end of a multi-core optical fiber, and light emitted from the other end is shared by any core. In the optical output measuring device of the multi-core optical fiber that guides the conversion element and measures the optical output of each core based on the incident order of light to each core, the output of the photoelectric conversion element is amplified on the light receiving side. A first amplifier capable of largely changing the gain, a second amplifier connected in series with the gain, which can finely adjust the gain, and sampling and measuring a signal passed through the first and second amplifiers A measuring circuit for obtaining a value output; and a control circuit for controlling the gains of the first and second amplifiers. Inject light and measure at this time on the light receiving side An output is obtained, and the control circuit determines the gains of the first and second amplifiers in accordance with the measured value output, and with the gains of the first and second amplifiers thus determined, sequentially from each core. It is characterized in that the emitted light is measured.

[Action]

Before sequentially inputting light to each core wire on the light incident side of the multi-core optical fiber, light is simultaneously input to all the core wires, and the measured value output at this time is obtained on the light receiving side. The control circuit determines the gains of the first and second amplifiers accordingly. With the gains of these amplifiers determined in this manner, light is sequentially incident on each core. Therefore, the output signal of the photoelectric conversion element due to the light emitted from each core wire is amplified by these amplifiers and sent to the measurement circuit so that the input signal level of the measurement circuit falls within the measurement range. it can. In this case, since the gains of the first and second amplifiers are adjusted first and then fixed, the gains of the amplifiers are not adjusted for each signal corresponding to the light emitted from each core wire, and therefore, In addition, the time for gain adjustment can be saved, and the overall measurement time can be reduced. Further, the gain is largely adjusted by the first amplifier,
Since the gain is finely adjusted by the amplifier, the level of the signal input to the measurement circuit can be set to the level having the highest resolution.

【Example】

Next, an embodiment of the present invention will be described with reference to the drawings. In FIG. 1, an instantly stable multi-channel light source 11 is connected to one end of a multi-core optical fiber 2.
The multi-channel light source 11 is controlled by the microprocessor 12, and the light source for each channel is turned on in order, and when turned on, stable light is instantaneously incident on one core. At the other end of the multi-core optical fiber 2, one light receiving element (photoelectric conversion element such as a photodiode) 31 is optically coupled to all the cores via an appropriate optical system. That is, no matter which core wire emits the light, the emitted light is guided to the common light receiving element 31 and converted into an electric signal. The electric signal (light receiving signal) thus obtained is amplified by the range switching amplifier 32 and the gain control amplifier 33. The range switching amplifier 32 switches its gain step by step in a relatively large unit, whereas the gain control amplifier 33
This is for fine adjustment of the gain, which changes the gain stepwise or continuously within the unit of gain switching. The light receiving signal amplified through the range switching amplifier 32 and the gain control amplifier 33 is sent to an A / D converter 34, which is a measuring circuit, and is sampled at a predetermined timing and converted into a digital signal, thereby obtaining a signal level. The measured value output corresponding to the above is obtained. This measured value output is taken into the microprocessor 35 and transferred to the display device 36 or the recording device 37 for display or recording. The microprocessor 12 on the light source side is a multi-channel light source
11 controls to generate light of each channel as shown in FIG. That is, before the light sources of the respective channels of the multi-channel light source 11 are sequentially turned on with CH1, CH2, CH3,..., CHn and the optical signal for measurement is incident, a period in which the light sources of all the channels are simultaneously turned on is provided. After a certain light-shielding time, the light sources of each channel are sequentially turned on.After this, until CHn, all the channels are turned on again after a certain light-shielding time. The channel ON and the sequential ON of each channel are repeated. As a result, a light receiving signal as shown in FIG. 2 is obtained from the light receiving element 31. Based on the pattern of the light receiving signal, the microprocessor 35 on the light receiving side captures the signals of all the channels on as a synchronization signal, and controls the subsequent measurement operation of each channel. First, the signals when all the channels are on are output to the range switching amplifier 32, the gain control amplifier 33, and the A / D converter 34.
Through the microprocessor 35 and the signal level thereof is measured. Thus, the microprocessor 35 controls the gains of the range switching amplifier 32 and the gain control amplifier 33. As a result, A / D converter 3
The input level 4 can be set within the measurement range, and the level with the highest resolution of the A / D converter 34 can be set. When such gain adjustment is completed, the gains of these amplifiers 32 and 33 are fixed. After that, the signal of each channel is sequentially changed to CH1, CH2,
…, So that the signals of all channels ON are used as the synchronization signal and the sampling / A /
The microprocessor 35 controls the A / D converter 34 to perform the D conversion. In this way, a measured value output is obtained for each channel, and is displayed and recorded. Here, since the gain is fixed at the same value for all channels, no time is required for range switching, and the overall measurement time can be greatly reduced. In addition, since the gain is finely adjusted by the gain control amplifier 33, the high resolution part of the A / D converter 34 can be used, so that the measurement accuracy can be improved. In this way, even if the gain of each channel is the same, a normal multi-core optical fiber (especially a tape core, etc.)
In No. 2, since the loss in each core wire does not have a great difference, the level of the received signal does not greatly differ in each channel, and the level of the signal input to the A / D converter 34 is measured. It will not be out of range and unmeasurable.

【The invention's effect】

ADVANTAGE OF THE INVENTION According to the optical output measuring device of the multi-core optical fiber of this invention, while measuring the optical output of each core of a multi-core optical fiber in a short time, the measurement precision is improved using the high resolution part of a measuring circuit. be able to.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention, and FIG. 2 is a time chart of light output in the embodiment. 11: Instantaneous stable multi-channel light source, 12, 35: Microprocessor, 2: Multi-core optical fiber, 31: Light receiving element, 32: Range switching amplifier, 33: Gain control amplifier, 34: A / D converter, 36 …… Display device, 37 ……
Recording device.

Claims (1)

(57) [Claims] 1. A multi-core optical fiber, in which light is sequentially incident on one core from one end, and light emitted from the other end is guided to a common photoelectric conversion element regardless of the core, and In a multi-core optical fiber optical output measuring device that measures the optical output of each core wire based on the order of incidence of light on the light receiving side, the output of the photoelectric conversion element is amplified to the light receiving side, and the gain can be largely switched. One amplifier and connected in series with it,
A second amplifier capable of finely adjusting the gain, a measurement circuit for sampling a signal passing through the first and second amplifiers to obtain a measured value output, and a control for controlling the gains of the first and second amplifiers Circuit, the light is simultaneously incident on all the cores before the light is sequentially incident on each core on the light incident side, and the measured value output at this time is obtained on the light receiving side,
The control circuit determines the gains of the first and second amplifiers in accordance with the measured value output, and in a state where the gains of the first and second amplifiers are determined, the light sequentially emitted from each core wire is determined. An optical output measuring device for a multi-core optical fiber, which performs measurement.