JPS5811915A - Optical transmission device - Google Patents

Abstract

PURPOSE:To improve the using efficiency of light and to expand the transmitting distance between terminals by branching a part of the light transmitting through optical fibers into a terminal changing the branched percentage variously to reduce insersion losses on the way of transmission. CONSTITUTION:Fibers 9-12 are arrayed one-dimensionally with equal intervals and adhered to the end surface of a focusing rod lens 5 having 1/4 period length and the fibers 10 and 12 are symmetrical to a lens axis 6. In the other end of the lens 5, a mirror 7 is adhered to a half surface of the lens 5 and a mirror 8 is movable. When the mirror 8 is parallel with the end surface of the lens 5, a part of the lght projected from the fiber 10 is reflected by the mirror 7, the remaining light is reflected by the mirror 8 and both the reflected light is made incident to the fiber 12. If the mirror 8 is inclined, the light reflected by the mirror 7 is made incident to the fiber 12 and the light reflected by the mirror 8 is reflected by the fiber 12. The light incident from the fiber 9 and reflected by the mirrror 8 is made incident to the fiber 12. By siad configuration, insertion losses are reduced, the using efficiency of light is improved and the transmission distance is expanded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical transmission device that efficiently propagates an optical signal propagating through an optical fiber to a terminal device and efficiently inserts an optical signal from the terminal into the optical fiber.

In an optical transmission device having multiple terminals, there is a conventional method of transmitting information by inputting and outputting part of the light in an optical fiber, for example, as shown in FIG.

1a, 1b, 1c, 1d, . . . are terminal devices, and the terminals are connected by a trunk optical fiber 4, and a typical example inside the terminal is shown in 1c. 2 is a branching device that transmits a part of the light in the optical fiber to the terminal, and since the amount of light branched from the trunk optical fiber 4 to the terminal is constant, The amount by which propagating light is attenuated when passing through a terminal is constant. Therefore, assuming that the light emission level at each terminal is the same, out of the light received by terminal 1c, terminal 1
The signal light intensity of a and the signal light intensity of 1b are different, and in the configuration shown in FIG. 1, the intensity of the light emitted from the terminal immediately to the right of the receiving terminal is the weakest. Therefore, in this dataway, it is necessary to set the minimum light reception level at the terminal to the above-mentioned light intensity. In reality, the minimum light receiving level is determined by the type of light receiving element and the light modulation method, and when a terminal attempts to receive light exceeding the minimum light receiving level, the amount branched from the main optical fiber 4 to the light receiving element is I have to do a lot. However, if the amount of branching is increased, the attenuation of the light passing through the terminal will increase and the light will be shunted. Not only are the above contradictory, but this dataway system has the drawbacks of poor light usage efficiency and short transmission distances between terminals.

In order to solve the above-mentioned drawbacks, the present invention changes the amount of branching from the trunk optical fiber into the terminal. below,
An embodiment of the present invention will be described with reference to the drawings. Second
The figure shows the branch and mixer in the terminal equipment.
The state of a) is when this terminal is not used, and the state of (b) is when this terminal is not used.
) indicates that this terminal is in use. In state (a), when the light propagating through the trunk optical fiber passes through the terminal, it is attenuated (passes 100%).On the other hand, (
In state b), half of the light propagating through the main optical fiber is branched to the light-receiving element side, the remaining half of the light is transmitted as is through the main optical fiber, and half of the light emitted from the light-emitting element is transmitted into the main optical fiber. be done. in this way,! By branching out the light in the main optical fiber as necessary, without attenuating the light at terminals that are not in use, it is possible to eliminate extra loss during transmission and improve the efficiency of light usage. I can do it.

However, since there was no efficient optical device having the functions shown in FIG. 2, it was not possible to construct the above-mentioned optical transmission apparatus. FIG. 3 shows the configuration of an optical device (hereinafter referred to as T-kagura) having such a function. Fibers 9 to 12 are bonded to the end face of a focusing rod lens 5 having a period length of 1/4. The fibers 10 and 12 are arranged in one dimension at equal intervals, and the fibers 10 and 12 are symmetrical about the lens axis 6. At the other end of the lens, a mirror 7 is glued to one half of the lens, and mirror 8 is movable. First, when the mirror 8 is parallel to the lens end face as shown in (a), part of the light emitted from the fiber IO is reflected by the mirror 7, the remaining light is reflected by the mirror 8, and both lights enter the fiber 12. incident. Next, when the mirror 8 is tilted as shown in FIG. 8B, the light reflected by the mirror 7 enters the fiber 12, but the light reflected by the mirror 8 enters the fiber 11.

Further, among the light incident from the fiber 9, the light reflected by the mirror 8 enters the fiber 12. As explained above, by using the fibers 10 and 12 as trunk optical fibers, using the fiber 11 as the light receiving element side and the fiber 9 as the light emitting element side, the T-coupler described in FIG. 2 can be realized. That is, by setting the terminal to the state (a) when it is not used and the state (b) when the terminal is used, insertion loss during transmission can be reduced.

The T Kagura explained above has the amount of light splitting (a).

Although there are only two states (b), an example of a T-cassilla in which the amount of branching can be changed continuously is shown in FIG. The same parts as in Figure 3 are given the same numbers. The reflecting mirror 8 is inclined with respect to the lens axis, and is fixed so that the light emitted from the fiber 10 enters the fiber 11 when reflected by the reflecting mirror 8. The mirror 7 is perpendicular to the lens axis and can be moved up and down. With this configuration, fiber 1
The amount of light incident from 0 to the fiber 11 decreases as the mirror 7 is moved upward, and on the contrary, the amount of light that enters the fiber 11 increases as the mirror 7 is moved downward. Therefore, by using this T-kagura, it is possible to arbitrarily change the amount of light transmitted through the trunk optical fiber (5) to the terminal.

As explained above, in an optical transmission device configured to branch part of the light propagating through an optical fiber into a terminal, insertion loss in the middle of the transmission path can be reduced by making the amount of branching to the terminal variable. Since it can be significantly reduced, it is possible to increase the efficiency of optical use and increase the transmission distance between terminals.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a conventional transmission device, and FIG. 2 is a configuration diagram of an optical functional device. 1a to 1d... terminal device, 2... turnout, 3...
Mixer, 4... Trunk optical fiber, 5... Rod lens, 7.8... Mirror, 9-12... Fiber. Patent Applicant Matsushita Electric Industrial Co., Ltd. Agent Hisashi Hoshino (6) Figure 1 (al (bl Figure 3 (G) (bl Figure 4) 1+ 87-

Claims (1)

[Claims] A plurality of terminals are coupled by optical fibers, and an optical branch/adder is capable of branching a part of the light propagating through the optical fiber into the terminal and inserting a part of the light emitted from the terminal into the optical fiber. What is claimed is: 1. An optical fiber transmission device having a variable branching ratio between light propagating through the optical fiber and light branching into a terminal.