JPH11119056A - Unpolarized light source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent unpolarized light and projection light from varying in quantity by connecting a light source and the polarizer of a depolarizer by one polarization plane maintaining optical fiber. SOLUTION: The unpolarized light source which projects unpolarized light by making the linear polarized light from a light source 11 incident on the depolarizer has a connection between the light source 11 and the polarizer 26 of the depolarizer by one polarization plane maintaining fiber 12. Namely, the polarization plane maintaining fiber 12 for projection of the light source 11 is connected directly to the polarizer 26. To match the planes of polarization of the polarization plane maintaining fiber 12 and polarizer 26, they are fixed mutually after their angles are adjusted so that the quantity of the projection light of an optical coupler 31 becomes maximum. Thus, the polarization plane maintaining fiber 12 for projection of the light source 11 is fixed and connected directly to the polarizer of the depolarizer and no optical connector is interposed between them, so the angle of the optical connector need not be adjusted. Further, there is no angle deviation between the incidence side and projection side of the optical connector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical communication system, for example,
The present invention relates to a non-polarized light source that is used for an optical fiber gyro or the like and emits linearly polarized light without polarization by a depolarizer.

[0002]

2. Description of the Related Art FIG. 2A shows a conventional non-polarized light source. A terminal of a polarization-maintaining optical fiber 12 for emitting light from a light source 11 such as a laser diode is connected to an incident side of a depolarizer 14 by an optical connector 13, and a single-mode optical fiber 16 is connected to an emitting side of the depolarizer 14 by an optical connector 15. Connected. Non-polarized light is emitted from the single mode optical fiber 16. If necessary, the unpolarized light is amplified by an erbium-doped optical fiber amplifier 17, and the amplified light is emitted to a single mode optical fiber 18. A part of the amplified light is split by the optical splitter 19, converted into an electric signal by the light receiving element 21, and applied to the optical amplifier according to the output of the light receiving element 21 so that the level of the electric signal becomes constant. The power of the excitation light of the excitation light source 22 is controlled, that is, the power of the emitted light is made constant.

The depolarizer 14 is, for example, an optical connector 13
The light from the polarization-maintaining optical fiber 25 connected to the polarization-maintaining optical fiber 25 is incident on the polarizer 26, the polarizer 26 extracts linearly polarized light, passes through the polarization-maintaining optical fiber 27, and is incident on the beam splitter 28. One light split by the beam splitter 28 enters the optical coupler 31 through the single mode optical fiber 29, and the other light split into two passes through the coil 32 made of the single mode optical fiber and passes through the optical coupler 3.
1 is incident. At this time, the two lights incident on the optical coupler 31 are given a sufficiently large phase difference so that there is no correlation with each other. The optical puller 31 combines the two incident lights and enters the optical connector 15 through the single mode optical fiber 33.

The transmission polarization plane (polarization direction) of the polarizer 26 and
By adjusting the polarization planes (polarization directions) of the polarization-maintaining optical fibers 25 and 27 so as to match each other, these three are fixed to each other. As the optical connector 13, FC / PC (screw-in type) and SC / PC (simply plug-in type) are generally used. Beam splitter 28-2
With one of the divided lights blocked, the input side and the output side of the optical connector 13 are relatively rotated about their axes so that the power of the output light of the optical connector 15 is maximized. In order to maximize the optical coupling in the optical connector 13, it is used.

[0005]

The prior art requires adjustment of the polarization plane (polarization direction) of the joint of the optical connector 13, and this adjustment is relatively troublesome. Due to vibration or repeated changes in the ambient temperature, the adjustment state of the optical connector 13 may be deviated.
For example, the light incident on the polarizer 26 deviates from the state where the planes of polarization match as shown by the solid line in FIG. 2B as shown by the broken line, and the transmitted light amount of the polarizer 26 decreases by ΔP.

When the optical amplifier 17 is provided with an automatic power adjustment function, the amount of light emitted from the optical fiber 18 can be kept constant. However, when vibration or shock is applied to the depolarizer 14 or an external object comes into contact with the polarization-maintaining single-mode fiber 12 on the incident side of the optical connector 13 and is suddenly twisted or bent, the polarization is also caused by these. Even if the plane of polarization of the light incident on the element 26 suddenly shifts, causing a sharp decrease in the light amount, the automatic light amount adjustment function of the optical amplifier 17 of this type does not follow.

[0007]

According to the present invention, the light source and the polarizer of the depolarizer are connected by one polarization-maintaining optical fiber.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention by assigning the same symbols to parts corresponding to those in FIG. In this embodiment, the polarization maintaining optical fiber 12 for emission of the light source 11 is directly connected to the polarizer 26. In order to match the polarization planes of the polarization-maintaining optical fiber 12 and the polarizer 26, the two are angle-matched so that the amount of light emitted from the optical coupler 31 is maximized, and then fixed to each other.

Although the optical amplifier 17 is not provided with an automatic light amount adjusting function in the drawing, it is apparent that this function may be provided. The output optical fiber 33 and subsequent portions of the optical coupler 31 may be omitted. This optical fiber 33
May be connected to the optical amplifier 17 by the optical connector 15 as shown by a dotted line. Other types of depolarizers may be used.

[0010]

As described above, according to the present invention, the polarization maintaining optical fiber for emission of the light source 11 is directly fixedly connected to the polarizer of the depolarizer, and the optical connector is not interposed between them. Does not require connector angle alignment. Moreover, there is no possibility that the angle of the incident side of the optical connector is shifted from the angle of the outgoing side of the optical connector, and there is no possibility that the amount of unpolarized light varies. Also, even if shock or vibration is applied, or even if the polarization maintaining optical fiber 12 is bent or twisted,
There is no possibility that a polarization plane shift occurs between the polarization-maintaining single-mode fiber 12 and the polarizer 26, and no change occurs in the amount of emitted light.

An automatic light amount adjusting function can sufficiently cope with a gradual change in the emitted light amount based on the ambient temperature, a change with time, and the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2A is a diagram illustrating a conventional non-polarization source, and FIG. 2B is a diagram illustrating a state of displacement between a polarizer, a polarization-maintaining optical fiber, and a polarization plane.

Claims (1)

[Claims] 1. A non-polarized light source that emits linearly polarized light from a light source into a depolarizer and emits non-polarized light, wherein the light source is connected to a polarizer of the depolarizer by a single polarization-maintaining optical fiber. A non-polarized light source.