JPH0113590B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides information on the surrounding environment (e.g., temperature and humidity) at multiple locations using a single light source and transmission line, without using a power source at each location, and in a relatively simple manner. The present invention relates to an optical fiber multi-point measuring device for measuring and transmitting data using a method.

Traditionally, optical fibers have been used to detect and transmit environmental information, which poses no risk of ignition compared to electrical methods, and has good fire resistance and resistance to electromagnetic induction, making it an extremely reliable measurement and transmission method. It is well known that this is possible. By the way, when there are a large number of measurement points, in the usual method, one fiber must be drawn for each measurement point to collect data, which makes wiring cumbersome. In order to send a large amount of information through a single fiber, methods such as time division multiplexing and wavelength multiplexing of the information are used. By the way, such a method requires a device for time division multiplexing, a power source for driving the light emitting elements, etc. at each measurement point, and requires a separate power line or a battery. Also,
In places where there is a risk of ignition or where explosion-proofing is required, it is better to avoid using a power supply, even if it is of small capacity.

The present invention uses one light source and one fiber wire.
Although it is a book, it is possible to transmit environmental information from many places at the same time, and since no power source is used at the measurement point, it is possible to realize in a very simple way a measurement transmission system that does not have any concerns about ignition etc. It is something.

A schematic diagram of a configuration according to the present invention is shown in FIG. Light from a light source 1 having a somewhat wide spectrum is focused and made incident on the fiber 5-1. 1st
The configuration shown in the figure is an example in which a filter that selectively reflects light of a part of the wavelength is used.The light from the light source passes through a 3dB optical splitter 2 to separate the reflected light, and then passes through the fiber 5-2. It is sent to the measuring device 3 located at the first measuring point. The measuring device 3 includes a lens system 101 that converts fiber-emitted light into parallel light, and a first light wavelength selective reflection filter (hereinafter simply referred to as a reflection filter) configured to cross the optical path according to the surrounding environment.
Consists of 102. The specific configuration of this part will be explained in more detail with reference to FIG.

FIG. 3 shows an example of the configuration of a measuring device when the detected information is temperature. Light having a wide spectrum emitted from the fiber 8 is collimated by a self-occurring lens 9, condensed by a similar lens 10, and incident on the fiber 11. A selective reflection filter 12 is arranged across this collimated parallel optical path, and in this example, the reflection filter 12 is connected to one end of a bimetal 13 so as to be movable in parallel in the direction of the arrow in the figure. By adopting such a configuration, the bimetal 13 is bent under the influence of the ambient temperature, which causes the reflection filter 1 to bend.
The area where 2 crosses the optical path will change.

Assume now that the spectrum of the light source 1 is shown by the envelope in FIG. In FIG. 2, the horizontal axis is the wavelength of light, and the vertical axis is the intensity. Next, for example, if the center wavelength of the reflection filter is λ ₁ to _{λ 4} and the center wavelength of the reflection filter 102 of the measuring instrument 3 in FIG. 1 is λ ₁ in FIG. By detecting the amount of light of the wavelength component of λ ₁ of the reflected light, the ambient temperature of the measuring device 3 can be detected. On the other hand, the components of the transmitted light of this measuring device 3 other than the wavelength λ ₁ are hardly changed. Reflection filter 1 of next measuring instrument 4
Assuming that the center wavelength of 03 is λ ₂ , the reflected light from the measuring device 4 is transmitted to the light source side without being affected by the reflection filter 102 of the measuring device 3.

In this way, the reflected light from each measuring device is transmitted through the fiber that sends the emitted light from the light source 1 to the side opposite to the emitted light, and enters the 3 dB splitter 2. Here, each reflected light is sent to a spectrometer 6 by a fiber 5-5, and a photodetector group 7 of this spectrometer 6 placed at a spectral position relative to the center wavelength of each reflection filter detects the light intensity of each spectrum. In the example, the ambient temperature of each measuring device is detected.

Here, the spectral breadth of the light source 1, the wavelength selection characteristics of the reflection filter used in the measuring instrument, and the number of measurement points are closely related to each other. When it is desired to take a large number of measurement points, it is necessary to make the wavelength selection characteristic of the reflection filter steeper or to widen the spectral width of the light source. By the way, when the spectral width of the light source is widened, the wavelength transmission characteristics of the transmission system consisting of the fiber and these lenses may become a problem due to chromatic aberration of the transmission fiber and the lenses used in the measuring instrument. A device using a reflection filter has a feature that if the order of arrangement of the reflection filters is determined taking these into consideration, the amount of light reflected to the spectroscope can be made uniform.

The reflection filter may be one that utilizes multiple reflections of a multilayer film, for example. In addition, as the spectrometer 6, one using a simple prism or one using a diffraction grating can be used. All you have to do is choose something.

Further, at the end of the fiber in the example shown in FIG. 1, it is necessary to provide an absorber to prevent reflected light from occurring.

Although the example in FIG. 1 shows a detection/measurement system using reflected light from a reflective filter, it is of course possible to consider a method using transmitted light. In such a system, 3dB
The optical splitter 2 becomes unnecessary, and the light from the light source 1 is immediately sent to the measuring device 3 through the fiber, and a spectrometer and a photodetector group are provided at the final end. Note that at this time, instead of a reflection filter, a measuring device that selectively absorbs light of a specific wavelength may be used. Although this system requires fewer components, since the entire spectrum is transmitted over the same distance, the intensity of the spectrum incident on the spectrometer after transmission is uniquely determined. In addition, since the light source section and the detection section are located at different locations except when the transmission system is in a loop, maintenance becomes worse than when using reflection.

Next, the case where the measuring device detects something other than temperature will be explained. It is clear that anything that converts detection information into length or distance can be used in the present invention.

For example, regarding the method of detecting humidity, it is possible to use a material made of nylon or hair that expands and contracts with changes in humidity instead of the bimetal used in the previous example.

Next, it can also be used for vibration detection, in which case a vibrator with a reflection filter attached to the tip may be used. It is also obvious that it can be used immediately as a pressure gauge. In addition, by assigning the measurement locations and measurement targets for each wavelength in advance, it is possible to clearly understand where the conditions are.

As described above, the present invention makes it possible to measure and transmit ambient environment information (temperature/humidity, atmospheric pressure, vibration, etc.) at many locations without using a power source using one light source and one transmission optical fiber. A possible system can be provided. Furthermore, this system is most suitable as a measurement and transmission system for the surrounding environment within a building or at a distance comparable to indoors.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram of a fiber-type multi-point measuring device according to an embodiment of the present invention, FIG. 2 is a diagram showing the spectrum of the light source used in FIG. 1, and FIG. It is a figure showing an example of composition. DESCRIPTION OF SYMBOLS 1... Light source, 2... Brancher, 3, 4... Measurement part, 5-1 to 5-5... Optical fiber, 6... Spectrometer, 7... Detector group, 102, 103... Reflection filter.

Claims (1)

[Claims] 1. In a device that detects and transmits information on the surrounding environment at a certain point using an optical fiber, at least
A light source with a wide spectrum, a plurality of filters that selectively reflect or absorb different portions of the spectrum of the light source, means for moving the filter according to the surrounding environment, and 1. An optical fiber multi-point measuring device comprising means for spectrally reflecting or transmitting light of the filter, and a photodetector of the spectroscopic means disposed corresponding to the position of the reflection or absorption spectrum of the filter.