JPS6033529A - Optical passive parts - Google Patents

Abstract

PURPOSE:To reduce a leak of light and obtain a small-sized device by arranging plural optical fibers and a light reflector near the focal plane of a specific converging lens on both sides of the lens, and interposing a polarizing and separating filter between the lens and light reflector. CONSTITUTION:A spacer 17 is inserted so that fiber end surfaces are on one focal plane of the converging lens 16 whose pitch is less than 0.25, and a prism 19 and the polarizing filter 20 are provided between the lens 16 and reflecting mirrors 18a and 18b arranged near the other focal plane of the lens 16. Light incident from a fiber 15a is separated by the polarizing filter 20 into a P and an S wave, and the P wave is transmitted through the filter 20 and reflected by the reflecting mirror 18a to enter an optical fiber 15c. The S wave is passed through the filter 20 and reflected by the reflecting mirror 18a to enter an optical fiber 15b. There is not any discontinuous point which may cause diffusion on the optical path, so a leak of light is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to passive optical components such as a splitter that branches an optical signal transmitted through one optical fiber into a plurality of fibers.

2. Description of the Related Art Structures of Conventional Examples and Their Problems Recently, optical passive components such as optical branchers have been used in the field of optical communications. For example, the one shown in FIG. 1 is known as a conventional optical passive component. In the figure, 1 is a prism, and a semi-transparent film 2 is interposed between the prisms 1. Assuming that the light semi-transmissive film 2 is a half mirror, the light incident from the fiber 3a becomes parallel light by the condensing lens 4a. The light reflected by the half mirror (photoelectric 1 (transmissive film 2) enters the fiber 3b via the focusing rod lens/Il) and is transmitted! , : Light enters the fiber 30 via the converging rod lens 4C. This is a turnout. However, one drawback of this configuration is that it requires a plurality of optical passive components (J lenses), making the configuration complex. As an optical passive component that solved this drawback, there was a splitter having the configuration shown in FIG. In the figure, the optical fibers 5a, 5c are bonded to the focal plane of the lens 6, and the optical fibers 5a and 5b are connected symmetrically to the lens axis. 7.8 is a reflecting mirror τ゛;
On one of the reflecting mirrors 7, a reflective film is formed up to near the center of the lens 6, and no reflective film is formed on the other parts. The other anti 11 mirror 8 is completely anti! ) 1 film is formed.

Now, if light is incident from the optical fiber 7/river 5a, this light will once spread and become a parallel beam at one end of the lens 6. A part of this light is reflected by the reflecting mirror 7, passes through the lens 6 again, and enters the optical fiber 5b. On the other hand, the light not reflected by the reflecting mirror 7 is reflected by m
+ and enters the optical fiber 5C. Consider a case where this branching configuration is applied to the access coupler shown in FIG. 3. Here, the access coupler has the function of splitting the light incident from the terminal 9 into the terminal 10 and the terminal 12, and part of the light incident from the terminal 11 is emitted to the terminal 12.
Terminal 10 refers to an optical passive component in which light incident from terminal 1 does not exit to terminal 10. 13 is a half mirror. Figure 4 is the second
This is an optical fiber 5d added to the branching device having the configuration shown in the figure. Since a part of the light incident from the optical fiber 5d enters the optical fiber 5b, the optical fibers 5a, 5b, 5
By assigning terminals 9.12°io and 1i to terminals c and 5d, respectively, it can be seen that they have the functions shown in FIG.

However, in this configuration, light scattering occurs at the edge 14 of the reflection &117, and a part of the light leaks to the terminal 10 of the optical fiber 5C, and there is a drawback that there is a lot of light leakage from the terminal 11 to the terminal 10.

Actual measurement data shows that the leakage is -3-33dB. - On the other hand, in a configuration in which the reflecting mirror 7 is a half mirror, the leakage is reduced, but since the coupling from the optical fiber 5a to the optical fiber 5C passes through the half mirror twice, the leakage becomes 6 dB or more.

OBJECTS OF THE INVENTION The present invention solves the above-mentioned conventional drawbacks, and aims to reduce the leakage of light and downsize optical passive components such as access couplers and splitters.

[Structure of the Invention]] In order to accomplish the above objects, the optical passive component of the present invention includes a focusing rod lens, a plurality of optical fibers arranged near the focal plane on one end side of the lens, and the other end of the lens. This is an optical passive component consisting of a light reflector placed near the focal plane on the side, and a polarization separation filter is interposed between the 0.25 pitch J Rimochi 1 nons and the light reflector. be.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings (FIG. 5). Arrangement of optical fibers 15a to 15d-4
- is the same as the conventional example shown in FIG. 4, but the convergent rod lens 16 is shorter than 0.25 pitch, and the spacer 11 is inserted so that the fiber end face becomes the focal plane on one end side. A prism 19, 19 and a polarizing filter 20 are provided between the lens 16 and the reflection lens 18a, 18b arranged near the focal plane on the other end side of the lens 16. Unpolarized light incident from the fiber 15a is separated into P waves and S waves by the polarizing filter 20, and the P waves are separated by the filter 20.
is transmitted through the optical fiber 15c and reflected at the reflection @ 18b.
incident on . On the other hand, the S wave is reflected by the filter 20, reflected by the reflecting mirror 18a, and enters the optical fiber 15b.

Also, the P wave of the light incident from the optical fiber 15d enters the optical fiber 15b.

It is clear that this has the function of an access coupler. In this configuration, there are no discontinuous points in the optical path that would cause scattering, so
Leakage to 5c can be reduced. Actual measurements showed that the leakage was 113 dB.

Here, the effect of the spacer 17 will be explained.

When using a 0.25 pitch rod lens, the laser
5 - Increasing the distance between the lens end face and the reflecting mirror increases the fiber coupling loss. This relationship is shown in FIG. This graph shows the coupling loss versus the distance between the lens and the reflecting mirror, with the fiber end face d as a parameter. From this result, if a 0.18 p lens is used, the coupling loss is less than 1 dBJ even if the distance between the lens and the reflecting mirror is set to 1.54&I or less.

Conventionally, focusing rod lenses have generally had a pitch of 0.25, and it has been thought that the distance between the lens and the reflecting mirror cannot be kept very large. It is also clear that the optical passive component with this configuration is a 3 dB splitter using polarization separation.

Effects of the Invention As described above, according to the present invention, by reducing the number of parts, it is possible to provide a small and inexpensive optical passive component with low near-end leakage.

[Brief explanation of the drawing]

1 to 4 are block diagrams showing a conventional example, FIG. 5 is a block diagram showing an embodiment of the present invention, and FIG. 6 is a lens characteristic diagram. -6- 15a to 15d... optical fiber, 16... lens,
17...Spacer, 18a, 18b...Reflector, 1
9... Prism, 20... Polarizing filter representative Yoshihiro Morimoto-7- Figure 1 Figure 3 1? lθ l! Figure 4 Figure 5 Figure 6 J (171+

Claims (1)

[Claims] 1. Light composed of a focusing rod lens, a plurality of optical fibers arranged near the focal plane at one end of the lens, and a light reflector arranged near the focal plane at the other end of the lens. An optical passive component in which a polarization separation filter is interposed between a lens shorter than 0.25 pitch and a light reflector.