JPS6048938B2 - two-way communication device - Google Patents

Description

[Detailed description of the invention] This invention relates to improvements in bidirectional optical communication equipment.

Recently, the σ performance of optical semiconductor devices and optical fibers has improved markedly, and the development of optical denoising such as optical branch circuits has progressed, and research and development is being carried out in various places to put these into practical use, such as optical transmission systems. being bypassed. Conventionally, most of the optical transmission systems studied have been unidirectional optical communication systems consisting of an optical transmitter, an optical transmission line, and an optical receiver. A bidirectional optical communication system that has optical transceivers at both ends of a single optical transmission line is considered to be used for simple communications and subscriber systems, etc., and uses different wavelengths and, in some cases, the same wavelength. There is a relationship. Optical transceivers for two-way optical communication systems that use different wavelengths are constructed by inserting a so-called wavelength-selective dielectric filter between the light source and the optical fiber, similar to the combination of wavelength-multiplexed optical communication systems. It will come true. On the other hand, in the optical transceiver of the two-way optical communication system that uses almost the same wavelength, a semi-transparent mirror is inserted between the light source and the optical fiber, but it has the disadvantage of high insertion loss. Therefore, there was an urgent need to develop bidirectional optical communication equipment with compact, inexpensive, and highly reliable optical transceivers. 5. Therefore, an object of the present invention is to provide a bidirectional optical communication device that uses light of different wavelengths and substantially the same wavelength, and has a compact, inexpensive, and highly reliable optical transceiver at both ends of a single optical transmission line. There are things you can get.

According to the present invention, in bidirectional communication having an optical transmitter/receiver consisting of an optical transmission line, a light source, and a photodetector (10) at both ends of the optical transmission line, a signal from the optical transmission line is placed between the light source and the optical transmission line. It has a reflecting mirror with a small hole that focuses most of the emitted light onto the photodetector and allows the emitted light from the light source to pass through, and reflects the emitted light from the light source at the end face of the optical transmission path 15. A two-way communication device is obtained which is configured such that the emitted light does not enter the photodetector and does not return to the light source.

i Hereinafter, this invention will be explained in detail using the drawings.

)2θ FIG. 1 is a schematic diagram of the second embodiment of the present invention,
The optical axis of the emitted light 11 from the light source S is inclined within the numerical aperture of the optical fiber F with respect to the optical axis of the optical fiber F1.

After the light 11 emitted from the light source S passes through the small hole 30 of the reflecting mirror M), it is partially reflected by the entrance/exit surface 20125 of the optical fiber F, and passes through a small hole other than the small hole 30 provided in the reflecting mirror M. 31
Since the reflected light 12 escapes through the photodetector D, it does not enter the photodetector D. FIG. 2 is a schematic diagram of a second embodiment of the optical transceiver according to the present invention, in which the input/output surface 20 of the optical fiber F is inclined at an angle α with respect to the optical axis of the optical fiber F, and the light source S The optical axis of the light 11 emitted from the optical fiber F is inclined with respect to the optical axis of the optical fiber F. In particular, when the refractive index of the central axis of the optical fiber F is n, the light source S
When the optical axis of the light emitted from the light source S is set to the corneal cell In-' (Nsinα), the light 11 emitted from the light source S is efficiently input to the optical fiber F.

The light 12 reflected by the entrance/exit surface 20 of the optical fiber F escapes without being hit by the reflecting mirror M. In these first and second embodiments, it is sufficient that the reflecting mirror M has a size that can reflect most of the light emitted from the optical fiber F, and all of the light must be within the effective light receiving surface of the photodetector. It has a concave reflecting mirror to focus the light. Since the reflected light from the input end face of the optical fiber does not enter the light receiver nor return to the light source, the performance of the two-way communication device can be improved. Figure 1,
It is clear that a flat reflecting mirror and a focusing lens may be used in place of the concave reflecting mirror in the coupling of the first and second embodiments schematically shown in FIG.

Note that this focusing lens is not needed if the light-receiving area of the photodetector D is larger than the area when the two output lights from the input/output surface 20 of the optical fiber F reach the light-receiving surface of the photodetector. Needless to say. When the reflecting mirror M is made of a dielectric multilayer film, a reflectance of almost 100% can be obtained. If the loss of the reflective surface is allowed, a reflective film made of aluminum, chrome, etc. is also possible. The small holes 30 and 31 of the reflecting mirror M can be formed by providing small holes in a glass substrate, etc., on which a reflective film such as a dielectric multilayer film is attached, or by not providing small holes in this glass substrate, etc., and only reflecting the small holes. Just avoid adding a film. In these first and second embodiments, the light source S may be a semiconductor laser, a light emitting diode, a Nd:YAG laser, etc., and in particular, the divergence angle of the light emitted from the light source is made as small as possible, It is desirable to use, in combination with the light source, an element that converts the beam into a circular beam, such as a spherical lens, a circular lens, a convergent light transmitter, etc., which improves the excitation efficiency to the optical fiber F.

Further, the photodetector D may be a photodiode, an avalanche photodiode, or the like. As described above in detail, the present invention provides a two-way communication device that has advantages such as low loss, small size, low cost, and high reliability, and can be used for both different wavelengths and substantially the same wavelength. Obtainable.

[Brief explanation of drawings]

1 and 2 are both schematic diagrams of embodiments of the present invention, where S is a light source, M is a reflective film, N is a reflective film, F is an optical fiber, D is a photodetector, and K and L are Focusing light transmitter, 11
is the light emitted from the light source S, 12 is the reflected light from the input/output surface of the optical fiber F, 13 is the light beam from the light source S propagating in the convergent light transmission body K, and 20 is the input/output surface of the optical fiber F. ,3
0 and 31 are small holes of the reflecting mirror M.

Claims (1)

[Claims] 1. In a two-way communication device equipped with an optical transceiver consisting of a light source and a photodetector at both ends of an optical transmission line, a photodetector is installed between the light source and the optical transmission line to transmit most of the light emitted from the optical transmission line. 1. A two-way communication device comprising a reflecting mirror having a small hole that efficiently condenses light into a light source and allows light emitted from a light source to pass through.