JPS58200646A - Communication system by propagation of light in space - Google Patents

Abstract

PURPOSE:To perform the high-quality communication of information by means of the space propagation of an optical signal, by making the emission wavelength of the optical signal, which is outputted from the light source of a transmitter, to be a specific length. CONSTITUTION:A light transmitter-receiver 2 having a semiconductor laser element as its light source radiates an optical signal outputted from the laser element in the directional angle of, for instance, + or -60 deg. from the ceiling of a room 1 toward each light transmitter-receiver 5 of a terminal 4 arranged on a floor surface. For each light receiving part of the transmitter receiver 5, information communication is performed by the propagation of an optical signal having the wave length of 1.38-1.43mum. In this case, since the level of sunlight component with respect to the optical signal of the wavelength of 1.38-1.43mum is about 1/10, the background noise of the sunlight does not bother the optical signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical space propagation communication system that performs information communication by spatially propagating optical signals.

[Technical background of the invention and electric point between them]

-In recent years, information communication in which optical signals are transmitted via optical fibers has developed dramatically and is widely used in various systems. However, in optical signal communication using such optical fibers, expandability is limited due to the use of optical connectors and optical branching elements, and the cost of installing optical fiber cables increases.
Furthermore, the problem of movement between KFi information overconfidence devices has increased, and information communication using the above-mentioned optical signal propagation through space is attracting attention. Figure 1 is a schematic diagram of the nine local network F system that utilizes the spatial propagation of optical signals. Multiple information overconfidence is performed in the spatially propagated optical signal between each optical transmitter/receiver 5 of the terminal A.
It is. Incidentally, the ugly light distribution transmitter/receiver 2 is connected to a host device of a central control station (not shown).

However, according to this local area, Toyota, the above *1! s in the reachable range of the optical signal J in ix? By arbitrarily increasing the number of terminals 4, it is easy to move the terminals themselves and their installation locations.

By the way, conventionally, optical signals used for optical transmission have mainly been used for long-distance transmission using optical fibers.
Considering the absorption loss due to H, O, etc. in the optical fiber, a wavelength of approximately α95 μm is often used. Further, various researches have been conducted on semiconductor radar devices as light sources for obtaining optical signals having such emission wavelengths. However, in the spatial propagation of optical signals in the local area network, an increase in noise caused by background optical noise rather than the optical absorption loss poses a major problem. For this reason, even if the light source of a conventional optical transmitter is used as is, there are many problems in signal quality and other aspects when communicating information using optical space propagation.

[Purpose of the invention]

The present invention has been made in consideration of these circumstances, and its tenth purpose is to improve signal quality by reducing the adverse effects of background optical noise on information communication boxes that carry out spatial propagation of optical signals. It is an object of the present invention to provide a highly practical optical space propagation communication system that can be carried out effectively without causing deterioration.

[Summary of the invention]

This Ryumei uses an optical signal with a wavelength of 1.38 m to 1.43 μm as an optical signal to be propagated in space. For example, a quaternary compound semiconductor is used as a light source to transmit and output an optical signal of the above wavelength. This uses a laser element.

〔Effect of the invention〕

Thus, according to the present invention, the background light noise, which is particularly harmful to large amounts of sunlight, is significantly reduced, preventing an increase in background light noise, increasing the S/N, and reducing the required received light/4 watts. It becomes possible to perform high-quality information communication by reducing the amount of noise. Therefore, by taking advantage of this advantage, it is possible to easily form horizontal stripes on a wide variety of local area optical networks and networks, and a great practical effect can be achieved.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

For example, in the optical power converter shown in FIG.
．． It is characterized by having a value of 43 μmK. A light source capable of outputting all optical signals of such wavelengths is realized, for example, by a quaternary compound semiconductor radar device made of InGaAsP, the structure of which is shown in FIG. To explain this semiconductor radar element, n-type InP:a
An n-InP:SnIIt@crystal layer with an impurity concentration of 5×lO1 is formed on the m-semiconductor crystal substrate 11.
InG is grown on top of it to a thickness of about 0.4 μm.
An aAsP crystal is grown to form the Rede active layer 13, and furthermore, an impurity 1 on D is added to the layer 10'``ex-''.
A light-emitting diode with a double heterojunction structure is formed by growing a p-Ink:Zn crystal layer of about 100 to 100% as a clad layer 14, and further a p-InGaAsP:Zm crystal layer 15.
After growing, an electrode 11 is formed via an insulator 81g such as 101 to form a nine-element structure.

Note that 18 in the figure is an electrode provided on the back surface of the substrate 11.

According to such a semiconductor radar element, generally 1.00
It is possible to obtain an emission wavelength of about μm to 150J1m.
, 40 .mu.m stable Raded light t- is obtained. Further, the light output can be secured at about 4 to 5 tmW with an electric current of 250 tmA.

The optical transmitter/receiver JFi, which uses the semiconductor radar element as a light source, transmits the optical signal output from the radar element to 8
The light is emitted from the ceiling of No. 1!17 with a directivity angle of, for example, ±60' to each optical transceiver 5 of the nine terminals 4 installed on the floor EiiK. The optical transceiver 5 is configured to receive the optical signal at a directivity angle of, for example, ±15°.

Thus, here, from the light source of the optical transceiver 2 to the optical transceiver 5
For each light receiving part, wavelength 13g, #B ~ 1.43μm
Information communication is performed through the spatial propagation of optical signals.

Incidentally, the spatial propagation of the optical signal from the optical transmitter/receiver ξ installed on the floor to the optical transmitter/receiver 1 is also within the range of l, 38 μm to 1.43 μm.
However, in this case, it is preferable to vary the wavelength of the optical signal within the above wavelength range depending on the communication direction of the optical signal. It is also possible to vary the wavelengths of the signals within the above-mentioned range.

As described above, according to this method, which performs information communication by spatially propagating optical signals with wavelengths of 1.38 μm to 43 μm, there is no damage prevention effect from sunlight, which has the greatest influence as background noise light, and K11 quality is achieved. This makes it possible to perform high-quality optical information communication. That is, as shown in FIG. 3, the spectral distribution of sunlight is distributed over a wide range from a short wavelength region to a long wavelength region. however,#! The meter shown in Figure 3 indicates the acceptance angle of sunlight. However, as is clear from this spectral distribution, the sunlight component with one wavelength of 1311a+m to 1.43μm is α95μwh, which has been mainly used for optical communication in the past.

Level 1 This is extremely small compared to the wavelength component, and is at a level below L/I O. Also, the spectrum of sunlight is 180 mm.
It, ss^mo Kencho 4- is also very small.

Therefore, the optical signal wavelength used for optical communication is 1.38 μm.
If it is set to between 143 Jm and 143 Jm, it becomes possible to eliminate the influence of sunlight on a large scale. It is also possible to set the optical signal wave length in the range of 1.80 μm to 1.85 mK, but in this case, there is a problem in which the output intensity as a light source cannot be sufficiently secured as a semiconductor element.

7tJII4all#1 This shows the relationship between the transmission speed and the required received optical power when propagating an optical signal of wavelength α95Ja+ in space. It shows the characteristics of the case. As shown by this relationship, if background noise light exists, the required received optical power must be increased by that amount! However, by transmitting information using an optical signal with a wavelength that is not affected by sunlight as in this method, it is possible to keep the required received optical power as described above low.

Therefore, by using this method, it is possible to significantly eliminate the negative influence of background noise light, suppress noise, and perform information overconfidence through spatial propagation of high-quality optical signals. and,
a- Caleria Hikane.

This makes it possible to easily construct a network, and its practical advantages are very high.

It should be noted that the present invention is not limited to the above-mentioned embodiments.For example, the semiconductor radar device may be constructed using a quaternary compound semiconductor device other than h-1. It can also be applied to communications. *This invention can be modified and modified in various ways without departing from its gist.

[Brief explanation of the drawing]

The figure explains one embodiment of the present invention. Figure 1 shows a local area optical network to which the embodiment is applied.
10 configuration E, Nz, rlAriflikLssμm=
Figure 3 shows the structure of a semiconductor radar element as a light source that outputs a 143 μm optical signal, Figure 3 shows the spectral distribution of sunlight, and Figure 4 shows the relationship between the transmission speed of the optical signal and the required received light intensity. FIG. 2... Optical transceiver, J... Optical signal (Space Transmission 11i)
, 4... Terminal, 5... Optical transceiver, 11... Semiconductor crystal substrate, II... Radical active layer. Applicant's agent Patent attorney Takehiko Dane 21 figures 2 figures 7 Wavelength (pm) JIk Ki Liaoquan (bps)

Claims (1)

[Claims] (Li) When performing information communication by spatially propagating two optical signals from an optical transmitter to a predetermined optical receiver, the emission wavelength of the optical signal output from the light source of the optical transmitter is Optical space propagation communication system patented as having a wavelength of 1.38 μm to 1.43 μm. (2) The light source of the optical transmitter is a quaternary system that outputs radar light with a wavelength of 1.38 μm to 1.43 μm. The optical space propagation communication system according to claim 1, which comprises a compound semiconductor radar element.