JPS5816374B2 - optical communication equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to an optical communication device.

The amount of communication that must be handled by communication devices continues to increase, leading to the rapid development of high capacity communication devices.

Even with large-capacity devices operating between 10'1E (z and 1012 Hz), the increase in communication traffic is so rapid that it is expected that the system will reach saturation in the very near future.

In order to cope with the increase in communication volume in the future, 101
Large capacity equipment operating around 5Hz is required.

Such devices are called optical communication devices because the frequency of 1015 Hz is within the frequency spectrum of light.

Conventional conductive waveguides used at frequencies between 10"Hz and 10"Hz cannot be used to transmit information at carrier frequencies around 1015Hz when transmitting frequencies around 10"Hz. The transmission medium required for this, hereinafter referred to as an optical signal transmission line or simply a transmission line, may consist of a single optical waveguide or a bundle of such optical waveguides.

Optical waveguides typically consist of an optical fiber having a transparent core and a layer surrounding the core and made of a transparent or rad material with a lower refractive index than the core.

Although the theory of optical waveguides has been known for some time, it is only recently that practical optical waveguides that do not excessively absorb transmitted light have been developed.

Fixed facilities such as ships, aircraft, and buildings often require a communication network to connect multiple remotely located stations.

Various interconnection schemes similar to electrical systems may be utilized to establish an optical communication system between such stations.

Each station has a “hardwired connection” to each other station.
)5, but when the number of stations is large, the amount of optical signal transmission lines required is large (and therefore such a method is undesirable in terms of the cost of the transmission line and the space it occupies). Become.

Stations may be interconnected by loops or line-to-data buses, which greatly reduces the amount of optical signal transmission line required, but the large number of couplers required, as explained below, can cause losses. The problem is that it becomes large.

Therefore, an object of the present invention is to provide an optical communication device with low loss.

. Briefly stated, the present invention relates to an optical communication device having a plurality of stations to which information is to be transferred, in which a plurality of optical signal transmission lines are provided, each having a first end and a second end; The first end of the line is coupled to a corresponding one station, and the second end of the transmission line is connected to passive optical coupler means for receiving optical signals from the transmission line connected to any one station. and a portion of the signal is coupled to transmission lines associated with all other stations.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings, but prior to that, a conventional optical communication device and a coupler used therein will be described.

In situations where multiple stations are to be interconnected by optical signal transmission lines, optical lines or optical loop data buses may be constructed using such transmission lines.

Such an arrangement is similar to known electrical data buses.

FIG. 1 schematically shows a portion of a loop or line data bus.

In the case of a loop data bus, a number of stations 11 are connected to a common optical signal transmission line 10 which has no ends.

In principle, the data could cycle through the loop many times, but in practice, after completing one loop, the data is attenuated to such an extent that it is no longer detectable.

Optical signals are taken out of and into transmission line 10 by coupler 12 which is coupled to station 11 by transmission line 13.

The transmission within the loop may be unidirectional, for example with each station transmitting only in the direction of arrow 14, or each station transmitting in the direction of arrows 14 and 15.
It is bidirectional, transmitting in both directions as shown in .

A line data bus consists of a number of stations all connected at their ends to a common optical signal transmission line.

As with loops, transmission on line data buses can also be unidirectional or bidirectional.

However, if each station must communicate with each other, operation must occur in a unidirectional mode.

Each station associated with a loop or line data bus requires a coupler to couple optical signals to and from the main transmission line.

Each coupler requires one or more transmission line connectors, mixers, etc., which introduce losses.

A branch coupler suitable for use with loop or line-to-data buses is shown in FIG.
Elements similar to those in the figures are indicated by the same reference numerals with a dash.

The first portion of the transmission line 10' is connected to the first portion of the mixer rod 21.
A second portion of transmission line 10' is coupled to a first end face of mixer rod 22.

The second end faces of mixer rods 21 and 22 are interconnected by a first bundle 23 of optical waveguide fibers.

Bundles of optical waveguide fibers 24 and 25 connect the second end faces of mixers 21 and 22, respectively, to the first end face of a third mixer-y-rod 26.

Mixer rods 21, 22 and 26 are made of transparent material, and layer 27 of transparent rad material.
．． 28 and 29, respectively.

These layers 27, 28 and 29 form a light reflective interface with the surface of each rod.

Fiber bundles 31 and 32 are disposed between the second end face of mixer rod 26 and photodetector 33 and light source 34, respectively.
is connected.

As used herein, the term "transparent" means transparent to the wavelength of light being propagated through the optical signal transmission line.

The function of each mixer rod is to transfer optical signals from any fiber at one end face of that mixer rod to all fibers at the other end face by direct propagation as well as internal reflection from the interface between the core and cladding. distribution.

A portion of the optical signal propagating in either of the sections of transmission line 10' is coupled to the other section 10' by optical fiber bundle 23 and mixer rods 21 and 22.

The configuration shown in FIG. 2 is such that the optical signals from both portions of transmission line 10' are connected to mixer rods 21 and 22 to a mixer rod 26 which couples the optical signals from bundles 24 or 25 to a detector 33. and is coupled by the optical waveguide bundles 24 and 25, so it is unidirectional.

Similarly, the optical signal from the light source 34 is transmitted to the mixer rod 2.
6 into bundles 24 and 25, and propagation of the optical signal is initiated in both parts of transmission line 10'.

mixer rods 21 and 22 and transmission lines 10 thereto;
Losses occur in the connectors required to couple the .

In a system such as that shown in FIG. 1, signal attenuation due to connector or coupler insertion loss increases with the number of stations located between two talking stations.

Therefore, each station. It would be advantageous to provide an optical communication device in which an optical signal is allowed to propagate from one station to other stations without passing through a coupler.

The optical communication device of the present invention, which is schematically shown in FIG. 3, was developed based on advanced knowledge.

The plurality of stations 41 to 46 each have optical signal transmission lines 51 to 46.
56 to a common passive coupler 48.

Each station 41-46 is a mixer similar to rod 26 in FIG.
It may also have a rod.

For simplicity of illustration, only station 41 has such features;
The mixer rod 51 is connected to light sensing and a light source by optical waveguide bundles 58 and 59.

Coupler 48 is adapted to receive an optical signal from any one station and couple a portion of that signal onto a transmission line associated with each other station.

Two optical signal couplers that can be used in the device of the invention include a fourth
Shown in Figure A.

The coupler of FIG. 4A has a layer 6 of transparent or rad material.
It consists of a cylindrical mixer rod 61, which is a transparent light-conducting member 4 material, with a layer 62 disposed on its surface, and the refractive index of the layer 62 is smaller than that of the rod 61.

End faces 63 and 64 of rod 61 are polished and substantially orthogonal to the longitudinal axis of the rod.

A light reflective coating 65 is provided on the end face 63.

Support means 67 positions bundle 66 of optical signal transmission lines such that the longitudinal axis of the end portion thereof is substantially parallel to that of rod 61 and the end of the bundle is adjacent end surface 64 .

Therefore, one end of the optical signal transmission line is connected to the corresponding station, and the other end of the optical signal transmission line is connected to the end surface 6 of the rod 61, which forms a reflective surface.
3 via a rod 61, and is supported by a spaced apart and fixed relation to an end surface 63.

A layer 68 of index matching fluid may be disposed between the end of the transmission line and the end surface 64 to provide good optical coupling therebetween.

Each transmission line within bundle 66 is coupled to a different station.

The optical signal from any one station is propagated to the coupler, where it enters the mixer rod 61, where it is deposited on the end face 63 of the rod 61, either directly or by reflection from the interface between the rod 61 and the layer 62. The light propagates to the reflective surface acting as a mirror formed by the optically reflective coating 65, reflects from the mirror and propagates back to the end face 64 where it is distributed among all the transmission lines in the bundle 66.

The communication network configuration of the apparatus of FIG. 3 is somewhat similar to an electrical node, which requires electrical transmission lines or cables to be connected to a common point.

When applied to electrical systems, the impedance matching problems associated with this approach present great difficulties at high frequencies.

Therefore, electrical configuration is not seriously considered in the field of high speed data.

However, in the optical communication system, the problem of impedance matching does not occur because the optical communication network has a degree of freedom that the electrical communication network does not have.

Comparing the device of Figure 3 to a line or loop data bus, the optical star bus requires only one coupler and therefore suffers the least signal attenuation due to connector or coupler insertion loss. Recognize.

In the case of a loop or line data bus, the dB in the loop or line data bus is There are cases where the loss expressed by , must increase linearly with the number of stations.

In the device according to the invention, the signal power is divided equally between all stations, so that the loss in dB increases only logarithmically with the number of stations.

For a coupler to operate properly, a portion of the optical signal propagating on any one of the optical signal transmission lines connected to it must be coupled into each other optical signal transmission line.

Referring to FIG. 4B, a diagram useful in calculating the minimum length Lm of a cylindrical mixer rod having a circular cross section is shown.

Rod 61 must be long enough to be an effective mixer, ie, long enough to cause light from one waveguide fiber to illuminate all other fibers.

In order to satisfy this condition, the rod 61 directs a portion of the light emitted from a circumferentially arranged first optical waveguide, e.g. at point a, to the first optical waveguide. It must be long enough to reflect into the 20th optical waveguide, ie, the point, located in diametrical relation to the end face 64.

The first waveguide has a reflected beam 64b that illuminates the second waveguide.
emits a ray 64a that must be reflected from the center of the end face 63 to form a .

An angular deviation θ of the light beam 64a with respect to the axis of the first waveguide.

is known as the half-angle of incidence of the waveguide.

Since the end portion of the waveguide is parallel to the axis of the rod 61, the angle θ.

can also be measured relative to the axis of the rod.

Angle θ. is given by the following formula. However, nl is the refractive index of the core of the optical waveguide, n2 is the refractive index of the cladding of the optical waveguide,
n3 is the refractive index of the mixer rod 61.

The minimum length Lm that satisfies the above requirements for illuminating diametrically opposed waveguides is given by:

where d is the diameter of rod 61 required for the maximum cross-sectional dimension of the waveguide bundle terminating at end face 64.

A mixer rod with a length greater than length Lm will still adequately illuminate all waveguides coupled to it.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a part of a conventional communication device, FIG. 2 is a schematic diagram showing a coupler that can be used in the device of FIG. 1, and FIG. 3 is a schematic diagram showing an optical communication device of the present invention. Figure 4A is a cross-sectional view of a passive coupler that may be used in the apparatus of Figure 3; Figure 4B
The figure is a diagram illustrating the calculation of the effective minimum length of a cylindrical mixer rod so that the rays emitted from any fiber illuminate all other connected fibers. In the drawing, 41 to 46 are stations, 51 to 56 are optical signal transmission lines, 48 is a passive optical coupler, 61 is a mixer rod, and 6
5 each indicates a light reflective coating.

Claims (1)

[Claims] 1. In an optical communication device including at least three stations, a plurality of optical signal transmission lines, the number of which is equal to the number of the stations, are connected to the corresponding stations at one end and are connected to a parallel bundle at the other end. connected to one passive optical coupler configured as a common single unit shared by said at least three stations in an array, said optical coupler being connected to any one of said stations; a reflective surface and a transparent optically conductive surface for receiving optical signals from the optical signal transmission lines associated with the member, and supporting means for supporting the other end of the plurality of optical signal transmission lines in a fixed relationship with the end face facing the reflective surface, the light conducting member Optical communication characterized in that an outer circumferential surface is covered with a material forming a boundary surface for reflecting an optical signal from the optical signal transmission line incident on the outer circumferential surface and returning it into the photoconductive member. Device.