CN111239907A

CN111239907A - Structure for improving return loss performance of optical isolator and application thereof

Info

Publication number: CN111239907A
Application number: CN201811434780.5A
Authority: CN
Inventors: 贾旭; 郑熙; 罗良涛; 任策; 于光龙
Original assignee: Fuzhou Photop Optics Co ltd
Current assignee: Fuzhou Photop Optics Co ltd
Priority date: 2018-11-28
Filing date: 2018-11-28
Publication date: 2020-06-05
Also published as: WO2020107519A1

Abstract

The invention discloses a structure for improving the return loss performance of an optical isolator and application thereof. The invention lengthens the distance between the polarizer and the end face of the optical fiber in the optical isolator by increasing the interval of the optical material or the air gap, greatly reduces the intensity of scattered light which is back coupled to the optical fiber by the scattered light of the polarizer, obviously improves the RL performance of the isolator, and can reach the RL value of more than 40 dB.

Description

Structure for improving return loss performance of optical isolator and application thereof

Technical Field

The invention relates to the field of optical communication, in particular to a structure for improving the return loss performance of an optical isolator and application thereof.

Background

In optical communication, signal light passes through many different optical interfaces during transmission from a light source to a receiver, and at each optical interface, reflection occurs to different degrees, and return light generated by the reflection finally returns to the light source along a light path. When the intensity of the return light is accumulated to a certain degree, the light source is unstable, and the problems of frequency drift, amplitude variation and the like are caused, so that the normal operation of the whole system is influenced, which becomes an important problem to be solved. Thus, a nonreciprocal passive device-optical isolator only allowing light to transmit along the forward direction of the light path is provided

Optical isolators are a very important class of passive devices in fiber optic communications. Such devices allow light to be transmitted only in the forward direction, while blocking light transmitted in the reverse direction, and function similarly to diodes in electronics. Therefore, the optical isolator is widely used in the processes of transmitting, amplifying, transmitting and the like of optical signals as one of the main basic components of optical communication.

The existing free-space optical isolator has the main structure as shown in fig. 1, which is a single-stage optical isolator and a double-stage optical isolator. For a single-stage optical isolator, the light transmitting optical axes of the

polaroids

01 and 02 at two ends form an included angle of 45 degrees, the middle part is a 45-degree rotating sheet 03 which can be provided with a magnetic field or an external magnetic field, and forward conduction and reverse isolation can be realized according to the nonreciprocal characteristic of the rotating sheet; as shown in fig. 2, the dual-stage optical isolator is composed of

polarizers

01, 02 and 03 and two 45 °

rotators

04 and 05, the light transmission optical axes of the

polarizers

02 and 03 respectively form an included angle of 45 ° and 90 ° with respect to the polarizer 01, the rotators can be provided with magnetic fields or externally applied magnetic fields, forward conduction and reverse isolation can be realized according to the nonreciprocal characteristic of the rotators, and the dual-stage optical isolator has higher isolation degree than a single-stage optical isolator.

Several typical examples of applications are shown in fig. 3 or 4, which illustrate a single-stage optical isolator, where fig. 3 illustrates an isolator 01 bonded to a fiber stub or fiber ferrule assembly 02 to form a fiber mounting subassembly, and fig. 4 illustrates an isolator 01 bonded to a fiber array 02 to form a fiber array mounting subassembly, which are widely used in optical communication devices. As mentioned above, since the polarizer is at the entrance and exit ends of the isolator, the polarizer itself has a relatively serious light scattering, after the isolator is directly bonded to the end face of the optical fiber, the influence of the end face reflection is eliminated by coating or selecting glue with matched refractive index, and the like, the stronger scattered light can be coupled into the optical fiber; because the angle distribution of the scattered light is wide, the scattered light cannot be effectively eliminated by a traditional method of increasing the end face angle of the optical fiber head, so that the RL performance is poor due to strong scattered light back coupling, generally the RL can only reach 30dB, and the requirement of a high-speed optical device cannot be met.

Disclosure of Invention

The invention aims to provide a structure for improving the return loss performance of an optical isolator, which has the advantages of simple design, small volume, easiness in processing and mass production and low cost, and an application thereof.

In order to achieve the purpose, the invention adopts the following technical scheme:

the structure for improving the return loss performance of the optical isolator comprises an optical isolation unit, wherein an optical spacer is fixed on the end face of the optical isolation unit.

Further, the optical isolation unit is a single-stage optical isolator or a double-stage optical isolator.

Furthermore, the optical spacing piece is provided with a through hole which is communicated along the direction of the optical axis.

Further, the cross section of the through hole is circular, elliptical or polygonal.

Further, the material of the optical spacing sheet is optical glass, crystal, Si sheet, plastic or high molecular polymer.

Further, the optical spacing piece is a flat piece or an angular wedge piece.

Further, the optical spacing piece is connected with the optical isolation unit through an optical cement or glue bonding method; when the glue is adopted for connection, the glue comprises one or more of UV glue, thermal curing glue and dual curing glue.

The structure of the invention is bonded with an optical fiber head, an optical fiber array or an optical fiber ferrule assembly through glue to be used as an optical fiber assembly sub-piece of an optical communication transceiver.

By adopting the technical scheme, the invention has the following beneficial effects: by increasing the interval of optical materials or air gaps, the distance between the polarizer and the end face of the optical fiber in the optical isolator is lengthened, the scattered light intensity of the polarizer scattered light back-coupled to the optical fiber is greatly reduced, the RL performance of the isolator is remarkably improved, and the RL value can reach over 40 dB.

Drawings

The invention is described in further detail below with reference to the following figures and detailed description:

FIG. 1 is a side view of a prior art single stage optical isolator;

FIG. 2 is a side view of a prior art dual stage optical isolator;

FIG. 3 is a side view of a prior art optical isolator in use one;

FIG. 4 is a bottom view of a second prior art optical isolator;

FIG. 5 is a side view of a flat-type optical spacer of the present invention for use in a single stage optical isolator;

FIG. 6 is a side view of a flat-type optical spacer of the present invention in use in a dual-stage optical isolator;

FIG. 7 is a side view of a wedge type optical spacer of the present invention for use in a single stage optical isolator;

FIG. 8 is a side view of a wedge type optical spacer of the present invention in use in a dual stage optical isolator;

FIG. 9 is a side view of a through-hole plate type optical spacer of the present invention for use in a single stage optical isolator;

FIG. 10 is a side view of a through-hole plate type optical spacer of the present invention for use in a dual stage optical isolator;

FIG. 11 is a side view of a through-hole wedge type optical spacer of the present invention in use with a single stage optical isolator;

FIG. 12 is a side view of a through-hole wedge type optical spacer of the present invention in use in a dual stage optical isolator;

FIG. 13 is a side view of a first embodiment of the application of the present invention;

FIG. 14 is a bottom view of a second embodiment of the present application;

FIG. 15 is a side view of a third embodiment of the application of the present invention;

fig. 16 is a bottom view of a fourth embodiment of the present invention.

Detailed Description

As shown in one of fig. 5 to 8, the structure 1 for improving the return loss performance of the optical isolator includes an optical isolation unit 12, where the optical isolation unit 12 is a single-stage optical isolator or a two-stage optical isolator (the structure is prior art and is not described in detail), and an optical spacer 11 is fixed on an end face of the optical isolation unit 12.

The material of the optical spacer 11 may be optical glass, crystal, Si sheet, plastic, or high molecular polymer, which can transmit near infrared wavelength (main wavelength range is 0.8um-2 um).

For matching, the optical spacing piece 11 can be made into a flat piece or an angular wedge piece, and the optical spacing piece 11 is connected with the optical isolation unit 12 by an optical cement or glue bonding method; when the glue is adopted for connection, the glue comprises one or more of UV glue, thermal curing glue and dual curing glue. In order to reduce the Insertion Loss (IL), the optical spacer 11 may be eliminated by applying an anti-reflection film to the glue according to the difference in refractive index of the material, and if the refractive index of the cured glue is close to the refractive index of the material of the optical spacer 11, the anti-reflection film does not need to be applied.

As shown in one of fig. 9 to 12, the structure 1 for improving the return loss performance of the optical isolator according to the present invention includes an optical isolation unit 12, where the optical isolation unit 12 is a single-stage optical isolator or a two-stage optical isolator, and an optical spacer 11 is fixed to an end surface of the optical isolation unit 12. The optical spacer 11 is provided with a through hole penetrating in the optical axis direction, and the cross section of the through hole is circular, elliptical or polygonal.

For matching, the optical spacing piece 11 can be made into a flat piece or an angular wedge piece, and the optical spacing piece 11 is connected with the optical isolation unit 12 by an optical cement or glue bonding method; when the glue is adopted for connection, the glue comprises one or more of UV glue, thermal curing glue and dual curing glue. To reduce Insertion Loss (IL), the fiber endfaces and isolator polarizer endfaces may be coated with an antireflective coating.

Taking a double-stage optical isolator without a through hole as an example, the structure of the invention can be bonded with an optical fiber head, an optical fiber array or an optical fiber ferrule assembly through glue to be used as an optical fiber assembly sub-component of an optical communication transceiver. FIG. 13 is a side view of the assembly of a fiber optic head or ferrule assembly 2 with the structure 1 (a plate-type optical spacer) of the present invention; FIG. 14 is a bottom view of the assembly of the optical fiber array 2 and the inventive structure 1 (a spacer for flat sheets); FIG. 15 is a side view of the assembly of the fiber optic head or ferrule assembly 2 with the structure 1 (wedge-type optical spacer) of the present invention; fig. 16 is a bottom view of the optical fiber array 2 and the structure 1 (wedge-type optical spacer) of the present invention.

Due to the existence of the optical spacing piece or the gap, the novel optical isolator structure can improve the RL performance to be more than 40dB by selecting proper spacing or gap thickness.

The manufacturing method of the invention is as follows:

1. the optical material is processed into an optical spacing piece through optical processing procedures such as cutting, grinding, polishing and the like, and the optical spacing piece can be selectively plated with no film or a pair of air antireflection films or glue antireflection films according to requirements;

2. and (3) for the optical spacing sheet with the holes, after the step 1 is completed, processing a series of through holes on the optical spacing sheet through processes such as laser, mechanical processing or etching.

3. Combining a large polarizer (usually a square plate of about 11x11 mm), a Faraday rotator and an optical spacer with similar sizes into a whole by adopting glue or optical cement; if glue is used, one or more of heat curing glue, ultraviolet curing glue, dual curing glue and the like can be adopted.

4. And cutting the large sheet into small pieces with required sizes. Thus, the present invention was completed.

While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. The utility model provides an improve structure of optical isolator return loss performance, includes optical isolation unit, its characterized in that: and an optical spacing piece is fixed on the end face of the optical isolation unit.

2. The structure for improving the return loss performance of an optical isolator as claimed in claim 1, wherein: the optical isolation unit is a single-stage optical isolator or a double-stage optical isolator.

3. The structure for improving the return loss performance of an optical isolator as claimed in claim 1, wherein: and the optical spacing sheet is provided with a through hole which is communicated along the direction of the optical axis.

4. The structure for improving the return loss performance of an optical isolator as claimed in claim 3, wherein: the cross section of the through hole is circular, elliptical or polygonal.

5. A structure for improving the return loss performance of an optical isolator as claimed in claim 1 or 3, wherein: the optical spacing sheet is made of optical glass, crystals, Si sheets, plastics or high molecular polymers.

6. A structure for improving the return loss performance of an optical isolator as claimed in claim 1 or 3, wherein: the optical spacing piece is a flat piece or an angular wedge piece.

7. A structure for improving the return loss performance of an optical isolator as claimed in claim 1 or 3, wherein: the optical spacing piece is connected with the optical isolation unit through an optical cement or glue bonding method; when the glue is adopted for connection, the glue comprises one or more of UV glue, thermal curing glue and dual curing glue.

8. The use of the structure for improving the return loss performance of the optical isolator as claimed in claim 1, wherein: the optical fiber assembly is bonded with an optical fiber head, an optical fiber array or an optical fiber ferrule assembly through glue and used as an optical fiber assembly sub-piece of an optical communication transceiver.