JPH0496008A - Terminal for optical device - Google Patents

Abstract

PURPOSE:To stabilize the transmission loss and to reduce generated noises by greatly reducing the interference between a mode LP01 and a mode LP11 in a fiber by the stress of an adhesive. CONSTITUTION:The adhesive 5 varies in shrinkage force with its layer thickness. Therefore, when plural opening parts of a capillary member 2 are provided and a single-mode fiber 3 is fixed by using an epoxy adhesive, the shrinkage force has a distribution according with intervals of the opening parts and the single-mode fiber 3 is stressed periodically. The mode LP11 nearby the cutoff wavelength of the single-mode fiber 3 is weak in light confinement and when an external force is applied by bending the fiber, the force is easily transmitted to the fiber clad. Thus, the interference between the modes LP01 and LP11 in the fiber can greatly be reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a terminal for an optical device, and particularly to a short single terminal fixed to an optical device for optically connecting a single mode optical device and an optical connector. The present invention relates to an optical device terminal with a built-in mode fiber.

[Conventional technology]

Conventionally, this type of optical device terminal has a structure in which an optical fiber is held and fixed to a cylindrical member having an inner diameter slightly larger than the diameter of the optical fiber. Optical devices in which this type of optical device terminal is used include fixed optical attenuators, optical connectors, optical filters, and optical semiconductor modules.

[Problem to be solved by the invention]

In the conventional optical device terminal described above, when a single mode fiber is generally connected to another single mode fiber, an LP mode is generated due to axis misalignment of the connecting portion. When both ends of a short fiber are connected with a single-mode fiber, the LP and □ modes generated at the input end and the LPOI mode, which is a propagation mode, proceed while interfering within the fiber, and due to the axis shift of the output side fiber, ,LP
Due to the phenomenon of zero or more division into O mode and LPII mode, the coupling efficiency of light to the output side fiber has periodic characteristics with respect to wavelength.

When an optical device has such wavelength dependence, there is a drawback that the transmission loss of the optical device changes due to a slight change in the wavelength used. Furthermore, there is a problem in that slight fluctuations in wavelength are converted into fluctuations in light intensity when passing through an optical device, causing noise.

[Means to solve the problem]

The terminal for an optical device of the present invention has a single mode fiber with a cutoff wavelength approximately equal to the wavelength used, and an inner diameter slightly larger than the diameter of the optical fiber, and the single mode fiber is previously held and fixed inside with an adhesive. A capillary member, a terminal body disposed on the outer periphery of the capillary member so as to be coaxial with the core center of the single mode fiber, and a plurality of openings provided at predetermined intervals on the outer periphery of the capillary member. It is equipped with

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a sectional view of the area around the opening of an embodiment of the present invention, and FIG.
The figure is a sectional view of a fixed optical attenuator using this embodiment, and FIG. 3 is a sectional view of an optical connector using this embodiment.

In this embodiment, as shown in FIG. 1, a single mode fiber 3 is held and fixed by an adhesive 5 to the inner diameter part of a capillary member 2 having a plurality of openings 1 at predetermined intervals on the outer circumference. There is. Here, the single mode fiber 3 is
The cutoff wavelength is approximately equal to the wavelength used. When the adhesive 5 hardens, the contraction force of the adhesive is distributed in accordance with the period of the opening 1, and a periodic external force is applied to the single mode fiber 3. The LPII mode caused by the axis misalignment is transmitted through the single mode fiber 3.
This is near the cutoff wavelength of the light, and since light is only weakly confined within the core, it easily escapes into the cladding due to this external force. Furthermore, the LPo+ mode, which is a propagation mode, propagates within the core without being attenuated because the light is strongly confined within the core.

Next, two usage examples using this embodiment will be explained with reference to FIGS. 2 and 3.

FIG. 2 shows a fixed optical attenuator using this embodiment. A single mode fiber 3 is adhesively fixed to a capillary member 2 having a plurality of openings 1 at predetermined intervals on its outer periphery. The capillary member 2 is adhesively fixed to the terminal 4.
The outer periphery is cut so that it is coaxial with the core center of the built-in single mode fiber 3. One end surface 6a of the terminal 4 is optically polished to enable connection with an optical connector, and the other end surface 6b is obliquely polished. A terminal 7 having the same structure as the terminal 4 is butted with a precision sleeve so that the diagonally polished surfaces thereof face each other. The damping film 8 is sandwiched between the ends where they abut against each other.

When this optical fixed attenuator is actually used, both ends of terminal 4 and terminal 7 are connected to optical connectors.

FIG. 3 shows an optical connector using this embodiment.

A capillary member 2 has an inner diameter slightly larger than the optical fiber diameter and has an auxiliary optical fiber 9 previously held and fixed therein, and a ferrule is attached to the outer periphery of the capillary member 2 so as to be coaxial with the core center of this optical fiber. A main body 10 is disposed, and the capillary member 2 has two openings 11 at a predetermined interval approximately in the center in the longitudinal direction, and the fiber end surface 12 of the auxiliary optical fiber 9 is connected to the capillary member 2. The built-in optical fiber is adhesively fixed at a predetermined position in the opening 11 on the side of the auxiliary optical fiber, and the end face of this built-in optical fiber is filled with an optically transparent liquid matching agent 13. Furthermore, the capillary member 2 to which the built-in optical fiber is fixed
A plurality of openings 1 are provided at predetermined intervals.

〔Effect of the invention〕

As explained above, the present invention relates to an optical device having a built-in short single-mode fiber used to efficiently couple and connect a single-mode fiber to an optical device. It is characterized by having multiple openings in it, and the built-in optical fibers are fixed with adhesive. The adhesive used is an epoxy adhesive that has a relatively large shrinkage force when cured. In general, these adhesives have different shrinkage forces depending on the thickness of the adhesive layer. Therefore, if a capillary member has multiple openings and a single mode fiber is fixed using epoxy adhesive, the contraction force will be distributed according to the spacing of the openings, causing periodic effects on the single mode fiber. Adds stress. The LP mode near the cutoff wavelength of a single mode fiber is weakly confined, and when external force such as bending is applied to the fiber, it easily escapes into the fiber cladding. Therefore, due to the stress of the adhesive, the LP1t mode caused by the misalignment of the fiber axis escapes to the cladding.
Interference between LPol mode and LpH mode within the fiber can be significantly reduced.

Therefore, when this terminal is used in an optical device, it has the effect of stabilizing transmission loss and reducing noise generated by the optical device during transmission.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the area around the opening of an embodiment of the present invention, and FIG.
The figure is a sectional view of a fixed optical attenuator using this embodiment, and FIG. 3 is a sectional view of an optical connector using this embodiment. DESCRIPTION OF SYMBOLS 1... Opening part, 2... Capillary member, 3... Single mode fiber, 4... Terminal, 5... Adhesive, 6
a... One end surface, 6b... The other end surface, 7.
... Terminal of the same structure, 8 ... Attenuation film, 9 ... Auxiliary optical fiber, 10 ... Ferrule body, 11 ... 2
12... fiber end face, 13... matching agent.

Claims (1)

[Claims] a single mode fiber with a cutoff wavelength that is approximately equal to the wavelength used; a capillary member having an inner diameter slightly larger than the diameter of the optical fiber and in which the single mode fiber is previously held and fixed with an adhesive; A light comprising: a terminal body disposed on the outer periphery of the capillary member so as to be coaxial with the center of the core; and a plurality of openings provided at predetermined intervals on the outer periphery of the capillary member. Terminal for devices.