CN115629447B

CN115629447B - Four-in-one space light delay self-interferometer

Info

Publication number: CN115629447B
Application number: CN202211646995.XA
Authority: CN
Inventors: 赵义博; 王东; 陈东升; 上宇
Original assignee: Beijing Zhongkeguoguang Quantum Technology Co ltd
Current assignee: Beijing Zhongkeguoguang Quantum Technology Co ltd
Priority date: 2022-12-21
Filing date: 2022-12-21
Publication date: 2023-02-28
Anticipated expiration: 2042-12-21
Also published as: CN115629447A

Abstract

The invention belongs to the technical field of optical communication, and discloses a four-in-one spatial light delay self-interferometer which comprises a first non-polarization beam splitter, a first half wave plate, a polarization beam splitter, a first magneto-optical polarization rotation module, a second magneto-optical polarization rotation module, a first light beam shifter, a second light beam shifter, a 2*2 unequal-arm interferometer and a reflector set for reflecting each signal light, polarization components and each light signal.

Description

Four-in-one space light delay self-interferometer

Technical Field

The invention relates to the technical field of optical communication, in particular to a four-in-one space optical delay self-interferometer.

Background

In a coherent optical communication system, a local oscillator laser is not needed in a self-homodyne detection technology, and a path of delayed signal light is used for replacing local oscillator light, so that the receiving bandwidth of the system can be improved, and the complexity of a receiving end is reduced. However, after the signal light is transmitted to the receiving end through the optical fiber channel, the polarization may become random, thereby affecting the stability of the delayed self-interference result.

Among the commonly used solutions, the first one is to use a polarization controller to calibrate the polarization state of the received signal light in real time, for example, patent CN114690436a, the system is complicated and depends heavily on the polarization disturbance rate; the second is to use polarization diversity technology, such as the documents "Li J, et al a self-coherent receiver for detection of PolMUX coherent signals [ J ]. Optics Express, 2012, 20 (19): 21413-21433", by splitting the signal light into two components with mutually perpendicular polarizations for performing delay self-interference, 4 delay interferometers and 8 photodetectors and subsequent amplifying circuits are required, increasing the complexity of the system. Patent US20120224184A1 and document Li, jingshi, et al, "Four-in-one interferometer for coherent and self-coherent detection." Optics express 21.11 (2013): 13293-13304 will reduce the number of delay interferometers to 1 using free space devices, however, this scheme outputs 8 interfering optical signals, requires 8 photodetectors, and the subsequent electronic processing part is still complicated.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a four-in-one space light delay self-interferometer.

The technical scheme of the invention is realized as follows:

a four-in-one spatial light retardation self-interferometer comprises a first non-polarization beam splitter, a first half wave plate, a polarization beam splitter, a first magneto-optical polarization rotation module, a second magneto-optical polarization rotation module, a first beam shifter, a second beam shifter, a 2*2 unequal-arm interferometer and a reflector set,

the beam splitting interface of the first non-polarization beam splitter and the polarization beam splitting interface of the polarization beam splitter are in the same plane;

the first non-polarization beam splitter is used for splitting the signal light input to the light beam incidence interface of the first non-polarization beam splitter to generate first signal light and second signal light which are respectively emitted from the light beam reflection interface and the light beam transmission interface of the first non-polarization beam splitter;

an included angle between the main axis direction and the horizontal direction of the first half-wave plate is 0 degree, the first half-wave plate is attached to a light beam transmission interface of the first non-polarization beam splitter and used for enabling the vertical polarization component of the second signal light to delay the phase pi relative to the horizontal polarization component;

the polarization beam splitter is used for carrying out polarization beam splitting on the first signal light to generate a first polarization component and a second polarization component; and a polarization beam splitter for polarization splitting the second signal light to generate a third polarization component and a fourth polarization component;

the 2*2 unequal arm interferometer is used for enabling the first polarization component and the second polarization component to respectively perform delayed self-interference, and respectively and correspondingly generating a first interference component, a second interference component, a third interference component and a fourth interference component of an in-phase component; the self-interference delay unit is used for enabling the third polarization component and the fourth polarization component to respectively perform delayed self-interference and respectively correspondingly generating a fifth interference component and a sixth interference component, a seventh interference component and an eighth interference component of the orthogonal phase component;

the first magneto-optical polarization rotation module is used for rotating the polarization of the second polarization component and the polarization of the third polarization component by 90 degrees, and is used for enabling the polarization of the second interference component, the third interference component, the fifth interference component and the eighth interference component to be unchanged when passing through;

the second magneto-optical polarization rotation module is used for enabling the polarization of the first polarization component and the fourth polarization component to be unchanged when the first polarization component and the fourth polarization component pass through, and is used for enabling the polarization of the first interference component, the fourth interference component, the sixth interference component and the seventh interference component to be rotated by 90 degrees;

the first beam shifter and the second beam shifter are used for enabling the horizontal polarized light signals passing through the first beam shifter and the second beam shifter to pass through linearly and enabling the vertical polarized light signals to be emitted after being shifted;

the reflector group is used for reflecting each signal light, each polarization component and each interference component;

the polarization beam splitter is also used for carrying out polarization beam combination on the first interference component and the third interference component to generate first interference output light; the second interference component and the fourth interference component are subjected to polarization beam combination to generate second interference output light; polarizing and combining the fifth interference component and the seventh interference component to generate third interference output light; and carrying out polarization beam combination on the sixth interference component and the eighth interference component to generate fourth interference output light.

Preferably, the mirror group comprises a first mirror, a second mirror, a third mirror, a fourth mirror, a fifth mirror and a sixth mirror, the reflecting surfaces of which are all parallel to the polarization beam splitting interface of the polarization beam splitter,

the first reflector is positioned above the first non-polarization beam splitter light beam reflection interface and used for reflecting the first signal light to enable the first signal light to vertically enter the lower part of the center of the first interface of the polarization beam splitter;

the second reflecting mirror is positioned on the right side of the beam transmission interface of the first non-polarization beam splitter and is used for reflecting the second signal light to enable the second signal light to vertically enter the center of the second interface of the polarization beam splitter;

the third reflector is positioned on the right side of the second beam deflector, corresponds to the lower part of the center of the third interface of the polarization beam splitter and is used for reflecting the first polarization component, the fourth interference component and the sixth interference component;

the fourth reflector is positioned above the first beam shifter, corresponds to the left part of the center of the fourth interface of the polarization beam splitter and is used for reflecting the second polarization component, the third polarization component, the second interference component and the eighth interference component;

the fifth reflector is positioned above the first magneto-optical polarization rotation module, corresponds to the right part of the center of the fourth interface of the polarization beam splitter and is used for reflecting the third interference component and the fifth interference component;

the sixth reflector is positioned at the right side of the second magneto-optical polarization rotation module, corresponds to the upper part of the center of the third interface of the polarization beam splitter and is used for reflecting the first interference component and the seventh interference component;

the length of the first beam shifter is less than the side length of the polarization beam splitter, and one end of the first beam shifter is aligned with a first interface of the polarization beam splitter and used for enabling the second polarization component and the second interference component to pass through linearly and enabling the third polarization component and the eighth interference component to be shifted and emitted;

the second beam shifter is equal to the first beam shifter in length, and one end of the second beam shifter is aligned with the second interface of the polarization beam splitter, so that the first polarization component and the fourth interference component pass through the second interface in a straight line, and the fourth polarization component and the sixth interference component are shifted and emitted.

Preferably, the mirror group comprises a first mirror, a second mirror, a third mirror, a fourth mirror, a fifth mirror and a sixth mirror, the reflecting surfaces of which are all parallel to the polarization beam splitting interface of the polarization beam splitting mirror,

the first reflecting mirror is positioned above the beam reflecting interface of the first non-polarizing beam splitter and used for reflecting the first signal light to enable the first signal light to vertically enter the upper part of the center of the first interface of the polarizing beam splitter;

the second reflecting mirror is positioned on the right side of the beam transmission interface of the first non-polarization beam splitter and is used for reflecting the second signal light to enable the second signal light to vertically enter the left part of the center of the second interface of the polarization beam splitter;

the third reflector is positioned at the right side of the second beam shifter, corresponds to the center of a third interface of the polarization beam splitter and is used for reflecting a fourth polarization component, a first interference component and a sixth interference component;

the fourth reflector is positioned above the first beam deflector, corresponds to the center of a fourth interface of the polarization beam splitter and is used for reflecting the third polarization component, the third interference component and the eighth interference component;

the fifth reflector is positioned above the first beam shifter, corresponds to the right part of the center of the fourth interface of the polarization beam splitter and is used for reflecting the second polarization component, the second interference component and the fifth interference component;

the sixth reflecting mirror is positioned at the right side of the second beam deflector, corresponds to the upper part of the center of the third interface of the polarization beam splitter and is used for reflecting the first polarization component, the fourth interference component and the seventh interference component;

the length of the first beam shifter is equal to the side length of the polarization beam splitter, and the first beam shifter is used for enabling the second polarization component, the second interference component and the third interference component to pass through linearly and enabling the third polarization component, the fifth interference component and the eighth interference component to be shifted and emitted;

the second beam deviator and the first beam deviator have the same length and are used for enabling the first polarization component, the first interference component and the fourth interference component to pass through linearly and enabling the fourth polarization component, the sixth interference component and the seventh interference component to be outputted in a deviant mode.

Preferably, the first magneto-optical polarization rotation module comprises a second half-wave plate and a first faraday optical rotation plate which are attached to each other, wherein an included angle between the main axis direction of the second half-wave plate and the horizontal direction is 22.5 degrees, and one side of the second half-wave plate, which is not attached to the first faraday optical rotation plate, is attached to a fourth interface of the polarization beam splitter; the polarization rotation angle of the first Faraday rotation plate is 45 degrees, and one side of the first Faraday rotation plate, which is not attached to the second half-wave plate, is attached to the first beam shifter;

the second magneto-optical polarization rotation module also comprises a second half-wave plate and a first Faraday rotation plate which are attached to each other, wherein the polarization rotation angle of the first Faraday rotation plate is 45 degrees, and one side, which is not attached to the second half-wave plate, of the first Faraday rotation plate is attached to a third interface of the polarization beam splitter; and one side of the second half-wave plate, which is not attached to the first Faraday optical rotation plate, is attached to the second beam shifter.

Preferably, the first magneto-optical polarization rotation module comprises a second faraday optical rotation plate and a third half-wave plate which are attached to each other, wherein the polarization rotation angle of the second faraday optical rotation plate is 45 degrees, and one side of the second faraday optical rotation plate, which is not attached to the third half-wave plate, is attached to the fourth interface of the polarization beam splitter; an included angle between the main shaft direction of the third half-wave plate and the horizontal direction is-22.5 degrees, and one side of the third half-wave plate, which is not attached to the second Faraday optical rotation plate, is attached to the first beam shifter;

the second magneto-optical polarization rotation module also comprises a second Faraday optical rotation plate and a third half-wave plate which are attached to each other, wherein one side, which is not attached to the second Faraday optical rotation plate, of the third half-wave plate is attached to a third interface of the polarization beam splitter; and an included angle between the main shaft direction of the third half-wave plate and the horizontal direction is-22.5 degrees, and one side, which is not jointed with the third half-wave plate, of the second Faraday optical rotation plate is jointed with the second beam shifter.

Preferably, the 2*2 interferometer comprises a second non-polarizing beam splitter, a first right angle prism, a second right angle prism, a quarter wave plate,

the beam splitting interface of the second non-polarization beam splitter and the polarization beam splitting interface of the polarization beam splitter are in the same plane, the fourth interface and the third interface of the second non-polarization beam splitter are respectively parallel to the inclined planes of the first right-angle prism and the second right-angle prism, the distances between the fourth interface and the inclined planes of the first right-angle prism and the second right-angle prism are unequal, and the distance difference is half of the arm length difference of the 2*2 unequal-arm interferometer;

the quarter wave plate is located at the position, close to the lower side, between the beam reflection interfaces of the second right-angle prism and the second non-polarization beam splitter and used for enabling the phase of the vertically polarized light signal passing through the quarter wave plate to be increased by pi/2 and the phase of the horizontally polarized light signal to be unchanged.

Preferably, the second rectangular prism is located on a one-dimensional displacement table, and the axial direction of the one-dimensional displacement table is perpendicular to the inclined plane of the second rectangular prism, so as to adjust the arm length difference of the 2*2 unequal-arm interferometer.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a four-in-one spatial light delay self-interferometer, which is characterized in that input signal light is divided into two paths, polarization beam splitting is respectively carried out, four paths of light signals are generated, delay self-interference is carried out on the four paths of light signals through the same unequal arm interferometer, then polarization beam combining is respectively carried out on interference results, polarization-independent delay self-interference in-phase components and orthogonal phase components can be obtained, demodulation signals are decoupled from an incident polarization state, only 4 paths of light signals are output, and active polarization compensation is not needed. The invention is suitable for signal light in any polarization state, has simple structure and higher stability.

Drawings

FIG. 1 is a schematic diagram of a first embodiment of a four-in-one spatial light delay self-interferometer of the present invention;

FIG. 2 is an optical path diagram of a first signal light (horizontal polarization component) of a four-in-one spatial light delay self-interferometer according to an embodiment of the present invention;

FIG. 3 is an optical diagram of a first signal light (vertical polarization component) according to an embodiment of the four-in-one spatial light delay self-interferometer of the present invention;

FIG. 4 is an optical path diagram of a second signal light (horizontally polarized component) according to an embodiment of the four-in-one spatial light delay self-interferometer of the present invention;

FIG. 5 is an optical diagram of a second signal light (vertical polarization component) according to an embodiment of the four-in-one spatial light delay self-interferometer of the present invention;

FIG. 6 is a schematic diagram of a second embodiment of a four-in-one spatial light delay self-interferometer of the present invention;

FIG. 7 is an optical path diagram of a second first signal light (horizontally polarized component) of an embodiment of the four-in-one spatial light delay self-interferometer of the present invention;

FIG. 8 is an optical diagram of a second first signal light (vertical polarization component) of a four-in-one spatial light delay self-interferometer embodiment of the present invention;

FIG. 9 is an optical diagram of a second signal light (horizontally polarized component) of a four-in-one spatial light delay self-interferometer according to an embodiment of the present invention;

FIG. 10 is an optical path diagram of a second signal light (vertical polarization component) of a four-in-one spatial light delay self-interferometer according to an embodiment of the present invention.

In the figure: 1-a first non-polarizing beam splitter, 2-a first half wave plate, 3-a polarizing beam splitter, 4-a first magneto-optical polarization rotation module, 4-1-a second half wave plate, 4-2-a first Faraday rotation plate, 4-3-a second Faraday rotation plate, 4-4-a third half wave plate, 5-a second magneto-optical polarization rotation module, 6-a first beam shifter, 7-a second beam shifter, 8-a first mirror, 9-a second mirror, 10-a third mirror, 11-a fourth mirror, 12-a fifth mirror, 13-a sixth mirror, 14-a second non-polarizing beam splitter, 15-a first right angle prism, 16-a second right angle prism, 17-a quarter wave plate.

Detailed Description

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments of the invention are shown.

A four-in-one spatial light retardation self-interferometer comprises a first non-polarization beam splitter 1, a first half wave plate 2, a polarization beam splitter 3, a first magneto-optical polarization rotation module 4, a second magneto-optical polarization rotation module 5, a first beam shifter 6, a second beam shifter 7, a 2*2 unequal-arm interferometer and a reflector set,

the beam splitting interface of the first non-polarization beam splitter 1 and the polarization beam splitting interface of the polarization beam splitter 3 are in the same plane;

the first non-polarization beam splitter 1 is configured to split a signal light input to a light beam incident interface thereof to generate a first signal light and a second signal light respectively emitted from a light beam reflection interface and a light beam transmission interface thereof;

an included angle between the main axis direction and the horizontal direction of the first half-wave plate 2 is 0 degree, and the first half-wave plate is attached to a light beam transmission interface of the first non-polarization beam splitter 1 and used for enabling the vertical polarization component of the second signal light to delay the phase pi relative to the horizontal polarization component;

the polarization beam splitter 3 is configured to perform polarization beam splitting on the first signal light to generate a first polarization component and a second polarization component; and a polarization beam splitter for polarization splitting the second signal light to generate a third polarization component and a fourth polarization component;

the 2*2 unequal arm interferometer is used for enabling the first polarization component and the second polarization component to respectively perform delayed self-interference, and respectively correspondingly generating a first interference component and a second interference component, a third interference component and a fourth interference component of an in-phase component; the self-interference delay unit is used for enabling the third polarization component and the fourth polarization component to respectively perform delayed self-interference and respectively correspondingly generating a fifth interference component and a sixth interference component, a seventh interference component and an eighth interference component of the orthogonal phase component;

the first magneto-optical polarization rotation module 4 is used for rotating the polarization of the second polarization component and the third polarization component by 90 degrees, and is used for enabling the polarization of the second interference component, the third interference component, the fifth interference component and the eighth interference component to be unchanged when passing through;

the second magneto-optical polarization rotation module 5 is used for keeping the polarization of the first polarization component and the fourth polarization component unchanged when passing through the first magneto-optical polarization rotation module, and is used for rotating the polarization of the first interference component, the fourth interference component, the sixth interference component and the seventh interference component by 90 degrees;

the first beam shifter 6 and the second beam shifter 7 are used for enabling the horizontal polarized light signals passing through the first beam shifter to pass through linearly and enabling the vertical polarized light signals to be emitted after being shifted;

the polarization beam splitter 3 is further configured to polarizedly combine the first interference component and the third interference component to generate first interference output light; polarizing and beam combining the second interference component and the fourth interference component to generate second interference output light; polarizing and combining the fifth interference component and the seventh interference component to generate third interference output light; and carrying out polarization beam combination on the sixth interference component and the eighth interference component to generate fourth interference output light.

The specific working principle is as follows:

the signal light in any polarization state can be written as

Wherein the content of the first and second substances,

the frequency, initial phase, and phase difference between orthogonal polarization components of the signal light, respectively.

The signal light is first incident perpendicularly to the beam incident interface of the first non-polarizing beam splitter 1, and is split into first signal light and second signal light at the beam splitting interface thereof. Wherein the first signal light has a polarization state of

The light is vertically incident to a first interface of the polarization beam splitter 3, and polarization beam splitting is performed to generate a horizontally polarized first polarization component and a vertically polarized second polarization component, which are respectively emitted from a third interface and a fourth interface of the polarization beam splitter 3. The first polarization component is still horizontally polarized after passing through the second magneto-optical polarization rotating module 5 and passes through the second beam shifter 7 in a straight line; the second polarization component is changed into horizontal polarization after passing through the first magneto-optical polarization rotating module 4 and passes through the first beam shifter 6 in a straight line; the polarization states of the two can be respectively written as

The first polarization component enters 2*2 unequal arm interferometer with horizontal polarization for delayed self-interference, and the first interference component and the second interference component are respectively generated

Wherein T is 2*2 and is not equal to the delay corresponding to the arm length difference of the arm interferometer.

The second polarization component reversely enters the 2*2 unequal arm interferometer in the horizontal polarization mode to carry out delay self-interference, and then a third interference component and a fourth interference component are generated respectively

The first interference component reversely passes through the second magneto-optical polarization rotation module 5 and then is polarized and rotated by 90 degrees to be vertically polarized; the third interference component is still horizontally polarized after reversely passing through the first magneto-optical polarization rotating module 4, and the third interference component and the third magneto-optical polarization rotating module reach the polarization beam splitter 3 at the same time for polarization beam combination, and the generated first interference output light is

The second interference component is still horizontally polarized after reversely passing through the first magneto-optical polarization rotating module 4; the fourth interference component reversely passes through the second magneto-optical polarization rotation module 5 and then is converted into vertical polarization, the fourth interference component and the vertical polarization reach the polarization beam splitter 3 at the same time for polarization beam combination, and the generated second interference output light is

The second signal light first passes through the first half-wave plate 2 and becomes polarized

Then, the light is vertically incident on the second interface of the polarization beam splitter 3, and polarization beam splitting is performed to generate a horizontally polarized third polarization component and a vertically polarized fourth polarization component, which are respectively emitted from the fourth interface and the third interface of the polarization beam splitter 3. The third polarization component is changed into vertical polarization after passing through the first magneto-optical polarization rotating module 4, and is deflected and emitted after passing through the first beam deflector 6; the fourth polarization component is still vertically polarized after passing through the second magneto-optical polarization rotating module 5 and is deflected and emitted after passing through the second beam deflector 7; the polarization states of the two can be respectively written as

The third polarization component enters 2*2 unequal arm interferometer with vertical polarization for delayed self-interference, and then a fifth interference component and a sixth interference component are generated

The fourth polarization component also reversely enters 2*2 unequal arm interferometer with vertical polarization for delayed self-interference, and a seventh interference component and an eighth interference component are generated respectively

The fifth interference component is still vertically polarized after reversely passing through the first magneto-optical polarization rotating module 4 and is changed into horizontally polarized light; the seventh interference component reversely passes through the second magneto-optical polarization rotation module 5 and then is polarized and rotated by 90 degrees, the seventh interference component and the second magneto-optical polarization rotation module simultaneously reach the polarization beam splitter 3 for polarization beam combination, and the generated third interference output light is

The sixth interference component reversely passes through the second magneto-optical polarization rotation module 5 and then becomes horizontal; the eighth interference component is polarized vertically after reversely passing through the first magneto-optical polarization rotating module 4, and the eighth interference component and the first magneto-optical polarization rotating module reach the polarization beam splitter 3 at the same time for polarization beam combination to generate fourth interference output light

It can be seen that the first interference output light to the fourth interference output light after the polarization beam combination are respectively phase difference components of 0 °, 180 °, 90 ° and 270 ° of the optical signal, and the polarization state transformation of the input signal light does not disturb the light intensity of each path of interference output light, so that the electrical signal converted from the light intensity signal of each path of interference output light by using the photodetector does not change with the change of the polarization state of the incident light signal, and the polarization-independent delayed self-interference of the optical signal can be realized. The arm length difference of the unequal arm interferometer can be adjusted by adjusting the one-dimensional displacement table, so that the unequal arm interferometer is suitable for different systems.

As shown in fig. 1 to 5, a first embodiment of the present invention:

the reflector group comprises a first reflector 8, a second reflector 9, a third reflector 10, a fourth reflector 11, a fifth reflector 12 and a sixth reflector 13, the reflecting surfaces of which are all parallel to the polarization beam splitting interface of the polarization beam splitter 3,

the first reflecting mirror 8 is located above the light beam reflecting interface of the first non-polarizing beam splitter 1 and used for reflecting the first signal light to enable the first signal light to vertically enter the lower part of the center of the first interface of the polarizing beam splitter 3;

the second reflecting mirror 9 is positioned at the right side of the light beam transmission interface of the first non-polarization beam splitter 1 and used for reflecting the second signal light to enable the second signal light to vertically enter the center of the second interface of the polarization beam splitter 3;

the third reflector 10 is located at the right side of the second beam shifter 7 and corresponds to the lower central portion of the third interface of the polarization beam splitter 3, and is used for reflecting the first polarization component, the fourth interference component and the sixth interference component;

the fourth reflecting mirror 11 is located above the first beam shifter 6, corresponds to the left part of the center of the fourth interface of the polarization beam splitter 3, and is used for reflecting the second polarization component, the third polarization component, the second interference component and the eighth interference component;

the fifth reflector 12 is located above the first magneto-optical polarization rotation module 4, corresponds to the right part of the center of the fourth interface of the polarization beam splitter 3, and is used for reflecting the third interference component and the fifth interference component;

the sixth reflecting mirror 13 is located on the right side of the second magneto-optical polarization rotation module 5, corresponds to the upper portion of the center of the third interface of the polarization beam splitter 3, and is used for reflecting the first interference component and the seventh interference component;

the length of the first beam shifter 6 is less than the side length of the polarization beam splitter 3, and one end of the first beam shifter is aligned with a first interface of the polarization beam splitter 3, so that the second polarization component and the second interference component can pass through the first beam shifter in a straight line, and the third polarization component and the eighth interference component can be shifted and emitted;

the second beam shifter 7 has the same length as the first beam shifter 6, and one end of the second beam shifter is aligned with the second interface of the polarization beam splitter 3, so as to pass the first polarization component and the fourth interference component straight through, and shift the fourth polarization component and the sixth interference component to exit.

The first magneto-optical polarization rotation module 4 comprises a second half-wave plate 4-1 and a first Faraday optical rotation plate 4-2 which are mutually attached, an included angle between the main shaft direction of the second half-wave plate 4-1 and the horizontal direction is 22.5 degrees, and one side, which is not attached to the first Faraday optical rotation plate 4-2, of the second half-wave plate is attached to a fourth interface of the polarization beam splitter 3; the polarization rotation angle of the first Faraday optical rotation plate 4-2 is 45 degrees, and one side, which is not jointed with the second half-wave plate 4-1, of the first Faraday optical rotation plate is jointed with the first beam shifter 6;

the second magneto-optical polarization rotation module 5 also comprises a second half-wave plate 4-1 and a first Faraday optical rotation plate 4-2 which are mutually attached, wherein an included angle between the main shaft direction of the second half-wave plate 4-1 and the horizontal direction is 22.5 degrees, and one side, which is not attached to the second half-wave plate 4-1, of the first Faraday optical rotation plate 4-2 is attached to a third interface of the polarization beam splitter 3; the side of the second half-wave plate 4-1 not attached to the first faraday rotation plate 4-2 is attached to a second beam shifter 7.

The 2*2 interferometer comprises a second non-polarizing beam splitter 14, a first right angle prism 15, a second right angle prism 16, a quarter wave plate 17,

the beam splitting interface of the second non-polarizing beam splitter 14 and the polarizing beam splitting interface of the polarizing beam splitter 3 are in the same plane, the fourth interface and the third interface are respectively parallel to the inclined planes of the first right-angle prism 15 and the second right-angle prism 16, the distances between the fourth interface and the third interface are different, and the distance difference is half of the arm length difference of the 2*2 unequal-arm interferometer;

the quarter-wave plate 17 is located at a position close to the lower side between the second right-angle prism 16 and the beam reflection interface of the second non-polarization beam splitter 14, and is used for increasing the phase of the vertically polarized light signal passing through the quarter-wave plate by pi/2 and keeping the phase of the horizontally polarized light signal unchanged.

The specific working principle of the embodiment is as follows:

the signal light in any polarization state can be written as

Wherein the content of the first and second substances,

The light beam is reflected by the first reflector 8 and then vertically incident to the first interface of the polarization beam splitter 3 for polarization beam splitting, so as to generate a first polarization component of horizontal polarization and a second polarization component of vertical polarization, which are respectively emitted from the third interface and the fourth interface of the polarization beam splitter 3, and the subsequent light path is as shown in fig. 2.

The first polarization component enters a second magneto-optical polarization rotation module 5, and the polarization state is changed into a polarization state after sequentially passing through a first Faraday optical rotation plate 4-2 and a second half-wave plate 4-1

I.e. still horizontally polarized, and passes through the second beam shifter 7 in a straight line; the second polarization component enters the first magneto-optical polarization rotation module 4, passes through the second half-wave plate 4-1 and the first Faraday optical rotation plate 4-2 in sequence and then changes into a polarization state

I.e. becomes horizontally polarized, and passes straight through the first beam shifter 6.

The first polarized component is reflected by the third reflector 10 and then vertically incident to the second interface of the second non-polarized beam splitter 14, and is split into two components with the same amplitude and polarization, wherein one component is reflected by the first right-angle prism 15 and then returns to the first non-polarized beam splitter 1, and the other component is reflected by the second right-angle prism 16 and then returns to the first non-polarized beam splitter 1 after passing through the quarter-wave plate 17. The other component is horizontally polarized, the phase is unchanged after passing through the quarter-wave plate 17, and after the two components are subjected to delayed self-interference, a first interference component and a second interference component are respectively generated

Wherein T is 2*2 delay corresponding to the arm length difference of the unequal arm interferometer.

The second polarization component is reflected by the fourth mirror 11 and then vertically incident to the first interface of the second non-polarization beam splitter 14, and is split into two components with the same amplitude and polarization, wherein one component is reflected by the first right-angle prism 15 and then returns to the first non-polarization beam splitter 1, and the other component is reflected by the second right-angle prism 16 and then returns to the first non-polarization beam splitter 1 after passing through the quarter-wave plate 17. Since the other component is horizontally polarized and has no phase change after passing through the quarter-wave plate 17, the two components generate a third interference component and a fourth interference component after delayed self-interference

The first interference component is reflected by the sixth reflector 13, reversely passes through the second magneto-optical polarization rotation module 5, sequentially passes through the second half-wave plate 4-1 and the first Faraday rotation plate 4-2, is polarized and rotated by 90 degrees and is changed into vertical polarization; the third interference component is reflected by the fifth reflector 12, reversely passes through the first magneto-optical polarization rotation module 4, sequentially passes through the first Faraday optical rotation plate 4-2 and the second half-wave plate 4-1 and then is still horizontally polarized, and simultaneously reaches the polarization beam splitter 3 for polarization beam combination, and the generated first interference output light is

The second interference component is reflected by the fourth reflector 11, then passes through the first beam shifter 6 in a straight line, then passes through the first magneto-optical polarization rotation module 4 in a reverse direction, and is still horizontally polarized after passing through the first Faraday optical rotation plate 4-2 and the second half-wave plate 4-1 in sequence; the fourth interference component is reflected by the third reflector 10, then passes through the second beam shifter 7 linearly, then passes through the second magneto-optical polarization rotation module 5 reversely, passes through the second half-wave plate 4-1 and the first Faraday optical rotation plate 4-2 in sequence, then is changed into vertical polarization, and reaches the polarization beam splitter 3 to be subjected to polarization beam combination, and the generated second interference output light is second interference output light

The optical path transmission process of the second signal light is as shown in fig. 3. The second signal light first passes through the first half-wave plate 2 and becomes polarized

Then vertically incident to the second interface of the polarization beam splitter 3, and performing polarization beam splitting to generate a horizontally polarized third polarization component and a vertically polarized fourth polarization component, which are respectively emitted from the fourth interface and the third interface of the polarization beam splitter 3. The third polarization component enters the first magneto-optical polarization rotation module 4, passes through the second half-wave plate 4-1 and the first Faraday optical rotation plate 4-2 in sequence and then changes into a polarization state

Namely, the vertical polarization is changed, and then the light beam is emitted in a deviation way after passing through the first light beam deviator 6; the fourth polarization component enters a second magneto-optical polarization rotation module 5, passes through a first Faraday optical rotation plate 4-2 and a second half-wave plate 4-1 in sequence and then has a polarization state of

I.e. still vertically polarized, and is deflected out after passing through the second beam deflector 7.

The third polarization component is reflected by the fourth mirror 11 and then vertically incident to the first interface of the second non-polarization beam splitter 14, and is split into two components with the same amplitude and polarization, wherein one component is reflected by the first right-angle prism 15 and then returns to the first non-polarization beam splitter 1, and the other component is reflected by the second right-angle prism 16 and then returns to the first non-polarization beam splitter 1 after passing through the quarter-wave plate 17. The other component is vertical polarization, the phase increases by pi/2 after passing through the quarter-wave plate 17, and after the two components are subjected to delayed self-interference, a fifth interference component and a sixth interference component are generated respectively

The fourth polarization component is reflected by the third reflector 10 and then vertically incident to the second interface of the second non-polarization beam splitter 14, and is split into two components with the same amplitude and polarization, wherein one component is reflected by the first right-angle prism 15 and then returns to the first non-polarization beam splitter 1, and the other component is reflected by the second right-angle prism 16 and then returns to the first non-polarization beam splitter 1 after passing through the quarter-wave plate 17. The other component is vertically polarized, the phase increases by pi/2 after passing through the quarter-wave plate 17, and after the two components are subjected to delayed self-interference, a seventh interference component and an eighth interference component are generated respectively

The fifth interference component is reflected by the fifth reflector 12, reversely passes through the first magneto-optical polarization rotation module 4, sequentially passes through the first Faraday optical rotation plate 4-2 and the second half-wave plate 4-1, and is still vertically polarized; the seventh interference component is reflected by the sixth reflector 13, reversely passes through the second magneto-optical polarization rotation module 5, sequentially passes through the second half-wave plate 4-1 and the first Faraday optical rotation plate 4-2, then is polarized and rotated by 90 degrees to be changed into horizontal polarization, and simultaneously reaches the polarization beam splitter 3 to be polarized and combined, and the generated third interference output light is

The sixth interference component is reflected by the third reflector 10, then is deflected by the second beam deflector 7 and then is emitted, then reversely passes through the second magneto-optical polarization rotation module 5, and is changed into horizontal polarization after sequentially passing through the second half-wave plate 4-1 and the first Faraday optical rotation plate 4-2; the eighth interference component is reflected by the fourth reflector 11, then deflected and emitted after passing through the first beam deflector 6, then reversely passes through the first magneto-optical polarization rotating module 4, is vertically polarized after sequentially passing through the first Faraday optical rotation plate 4-2 and the second half-wave plate 4-1, and simultaneously reaches the polarization beam splitter 3 for polarization beam combination, and the generated fourth interference output light is

It can be seen that the first to fourth interference output lights after polarization beam combination are respectively phase difference components of 0 °, 180 °, 90 ° and 270 ° of the optical signal, and the first interference output light and the second interference output light are photoelectrically converted by using the balanced detector, and the generated difference current is

Photoelectric conversion is performed on the third interference output light and the fourth interference output light by using a balanced detector, and a differential current is generated

Wherein, R is the response coefficient of the detector.

The output light intensity and the differential current are independent of the polarization state of the signal light, i.e. any fluctuation of the polarization state of the signal light will not affect the output differential current, and the receiving sensitivity of heterodyne detection will not be reduced. Therefore, the scheme of the invention does not need any active modulation and compensation, can eliminate the influence of the polarization state change of the signal light on the final output signal, and realizes stable delayed self-interference, thereby ensuring stable self-coherent detection.

As shown in fig. 6 to 10, the second embodiment of the present invention:

the first reflecting mirror 8 is positioned above the light beam reflecting interface of the first non-polarizing beam splitter 1 and used for reflecting the first signal light to enable the first signal light to vertically enter the upper part of the center of the first interface of the polarizing beam splitter 3;

the second reflecting mirror 9 is positioned on the right side of the light beam transmission interface of the first non-polarizing beam splitter 1 and used for reflecting the second signal light to enable the second signal light to vertically enter the left part of the center of the second interface of the polarizing beam splitter 3;

the third reflector 10 is located at the right side of the second beam shifter 7 and corresponds to the center of the third interface of the polarization beam splitter 3, and is used for reflecting a fourth polarization component, a first interference component and a sixth interference component;

the fourth reflecting mirror 11 is located above the first beam shifter 6 and corresponds to the center of the fourth interface of the polarization beam splitter 3, and is used for reflecting the third polarization component, the third interference component and the eighth interference component;

the fifth reflecting mirror 12 is located above the first beam shifter 6, corresponds to the right part of the center of the fourth interface of the polarization beam splitter 3, and is used for reflecting the second polarization component, the second interference component and the fifth interference component;

the sixth reflecting mirror 13 is located at the right side of the second beam shifter 7, corresponds to the upper part of the center of the third interface of the polarization beam splitter 3, and is used for reflecting the first polarization component, the fourth interference component and the seventh interference component;

the length of the first beam shifter 6 is equal to the side length of the polarization beam splitter 3, and is used for enabling the second polarization component, the second interference component and the third interference component to pass through linearly and enabling the third polarization component, the fifth interference component and the eighth interference component to be shifted and emitted;

the second beam shifter 7 has the same length as the first beam shifter 6, and is used for linearly passing the first polarization component, the first interference component and the fourth interference component, and shifting and outputting the fourth polarization component, the sixth interference component and the seventh interference component.

The first magneto-optical polarization rotation module 4 comprises a second Faraday optical rotation plate 4-3 and a third half-wave plate 4-4 which are mutually attached, the polarization rotation angle of the second Faraday optical rotation plate 4-3 is 45 degrees, and one side, which is not attached to the third half-wave plate 4-4, is attached to a fourth interface of the polarization beam splitter 3; an included angle between the main shaft direction of the third half-wave plate 4-4 and the horizontal direction is-22.5 degrees, and one side, which is not attached to the second Faraday optical rotation plate 4-3, is attached to the first beam shifter 6;

the second magneto-optical polarization rotation module (5) also comprises a second Faraday optical rotation plate (4-3) and a third half-wave plate (4-4) which are mutually attached, wherein one side, which is not attached to the second Faraday optical rotation plate 4-3, of the third half-wave plate 4-4 is attached to a third interface of the polarization beam splitter 3; an included angle between the main axis direction of the third half-wave plate 4-4 and the horizontal direction is-22.5 degrees, and one side, which is not jointed with the third half-wave plate 4-4, of the second Faraday optical rotation plate 4-3 is jointed with the second beam shifter 7.

The second right-angle prism 16 is positioned on a one-dimensional displacement table, and the axial direction of the one-dimensional displacement table is perpendicular to the inclined plane of the second right-angle prism 16, so that the arm length difference of the 2*2 unequal-arm interferometer can be adjusted.

The second embodiment has the following specific working principle:

the signal light in any polarization state can be written as

Wherein the content of the first and second substances,

respectively, the frequency of the signal light, the initial phase, and the phase difference between the orthogonal polarization components.

The light is reflected by the first reflector 8 and then vertically incident to the first interface of the polarization beam splitter 3 to perform polarization beam splitting, so as to generate a horizontally polarized first polarization component and a vertically polarized second polarization component, which are respectively emitted from the third interface and the fourth interface of the polarization beam splitter 3, and the subsequent light path is as shown in fig. 5.

The first polarization component enters a second magneto-optical polarization rotation module 5, and the polarization state of the first polarization component is changed into a polarization state after the first polarization component sequentially passes through a third half wave plate 4-4 and a second Faraday optical rotation plate 4-3

I.e. still horizontally polarized, and passes through the second beam shifter 7 in a straight line; the second polarization component enters the first magneto-optical polarization rotation module 4, and the polarization state is changed into a polarization state after sequentially passing through the second Faraday optical rotation plate 4-3 and the third half-wave plate 4-4

I.e. becomes horizontally polarized, passes straight through the first beam shifter 6.

The first polarization component is reflected by the sixth mirror 13 and then vertically incident to the second interface of the second non-polarization beam splitter 14, and is split into two components with the same amplitude and polarization, wherein one component is reflected by the first right-angle prism 15 and then returns to the first non-polarization beam splitter 1, and the other component is reflected by the second right-angle prism 16 and then returns to the first non-polarization beam splitter 1 after passing through the quarter-wave plate 17. The other component is horizontally polarized, the phase is unchanged after passing through the quarter-wave plate 17, and after the two components are subjected to delayed self-interference, a first interference component and a second interference component are respectively generated

The second polarization component is reflected by the fifth mirror 12 and then vertically incident to the first interface of the second non-polarization beam splitter 14, and is split into two components with the same amplitude and polarization, wherein one component is reflected by the first right-angle prism 15 and then returns to the first non-polarization beam splitter 1, and the other component is reflected by the second right-angle prism 16 and then returns to the first non-polarization beam splitter 1 after passing through the quarter-wave plate 17. The other component is horizontally polarized, the phase is unchanged after passing through the quarter-wave plate 17, and after the two components are subjected to delayed self-interference, a third interference component and a fourth interference component are respectively generated

The first interference component is reflected by the third reflector 10, then passes through the second beam shifter 7 in a straight line, then passes through the second magneto-optical polarization rotation module 5 in a reverse direction, and is polarized and rotated by 90 degrees after sequentially passing through the second Faraday rotation plate 4-3 and the third half-wave plate 4-4, so that the first interference component is changed into vertical polarization; the third interference component is reflected by the fourth reflector 11, then passes through the first beam shifter 6 in a straight line, then reversely passes through the first magneto-optical polarization rotation module 4, passes through the third half-wave plate 4-4 and the second Faraday optical rotation plate 4-3 in sequence and is still horizontally polarized, the third interference component and the second Faraday optical rotation plate simultaneously reach the polarization beam splitter 3 for polarization beam combination, and the generated first interference output light is the first interference output light

The second interference component is reflected by the fifth reflector 12, then passes through the first beam shifter 6 in a straight line, then passes through the first magneto-optical polarization rotation module 4 in a reverse direction, and is still horizontally polarized after passing through the third half-wave plate 4-4 and the second Faraday optical rotation plate 4-3 in sequence; the fourth interference component is reflected by the sixth reflector 13, then passes through the second beam shifter 7 linearly, then passes through the second magneto-optical polarization rotation module 5 reversely, passes through the second Faraday optical rotation plate 4-3 and the third half-wave plate 4-4 in sequence, then is changed into vertical polarization, and reaches the polarization beam splitter 3 to be subjected to polarization beam combination, and the generated second interference output light is second interference output light

The optical path transmission process of the second signal light is as shown in fig. 6. The second signal light first passes through the first half-wave plate 2 and becomes polarized

Then vertically incident to the second interface of the polarization beam splitter 3, and performing polarization beam splitting to generate a horizontally polarized third polarization component and a vertically polarized fourth polarization component, which are respectively emitted from the fourth interface and the third interface of the polarization beam splitter 3. The third polarization component enters the first magneto-optical polarization rotation module 4, and the polarization state is changed into a polarization state after sequentially passing through the second Faraday optical rotation plate 4-3 and the third half-wave plate 4-4

Namely, the polarization is changed into vertical polarization, and then the light beam is deflected and emitted after passing through the first light beam deflector 6; the fourth polarization component enters a second magneto-optical polarization rotation module 5, and the fourth polarization component sequentially passes through a third half wave plate 4-4 and a second Faraday optical rotation plate 4-3 to form a polarization state

The fifth interference component is reflected by a fifth reflector 12, then deflected and emitted by a first beam deflector 6, then reversely passes through a first magneto-optical polarization rotation module 4, and is still vertically polarized after sequentially passing through a third half-wave plate 4-4 and a second Faraday optical rotation plate 4-3; the seventh interference component is reflected by the sixth reflector 13, reversely passes through the second magneto-optical polarization rotation module 5, sequentially passes through the second Faraday rotation plate 4-3 and the third half-wave plate 4-4, is polarized and rotated by 90 degrees to be horizontal polarization, and simultaneously reaches the polarization beam splitter 3 to be polarized and combined, and the generated third interference output light is

The sixth interference component is reflected by the third reflector 10, then is deflected by the second beam deflector 7 and then is emitted, then reversely passes through the second magneto-optical polarization rotating module 5, and is changed into horizontal polarization after sequentially passing through the second Faraday optical rotation plate 4-3 and the third half-wave plate 4-4; the eighth interference component is reflected by the fourth reflector 11, then is deflected and emitted after passing through the first beam deflector 6, then reversely passes through the first magneto-optical polarization rotating module 4, is vertically polarized after sequentially passing through the third half-wave plate 4-4 and the second Faraday optical rotation plate 4-3, and simultaneously reaches the polarization beam splitter 3 for polarization beam combination, and the generated fourth interference output light is the polarization output light

Photoelectric conversion is carried out on the third interference output light and the fourth interference output light by using a balanced detector, and a differential current is generated

Wherein R is the response coefficient of the detector.

It can be known from the embodiments of the present invention that, the present invention provides a polarization-independent spatial light delay interferometer for use in auto-coherent detection, which performs polarization beam splitting on input signal light, so that two orthogonal polarization components perform delay self-interference respectively, transforms the polarization states of the two in the transmission process through a wave plate set, and uses a 4*4 polarization beam combining module to perform polarization beam combining on the interference results of the two, so as to obtain in-phase components and orthogonal phase components of the polarization-independent signal light delay self-interference, decouple a demodulation signal from an incident polarization state, and output only 4 optical signals without active polarization compensation. The invention is suitable for signal light in any polarization state, has simple structure and higher stability.

Claims

1. A four-in-one spatial light retardation self-interferometer is characterized by comprising a first non-polarization beam splitter (1), a first half wave plate (2), a polarization beam splitter (3), a first magneto-optical polarization rotation module (4), a second magneto-optical polarization rotation module (5), a first beam shifter (6), a second beam shifter (7), a 2*2 unequal-arm interferometer and a reflector set,

the beam splitting interface of the first non-polarization beam splitter (1) and the polarization beam splitting interface of the polarization beam splitter (3) are in the same plane;

the first non-polarization beam splitter (1) is used for splitting the signal light input to the light beam incidence interface of the first non-polarization beam splitter to generate first signal light and second signal light which are respectively emitted from the light beam reflection interface and the light beam transmission interface of the first non-polarization beam splitter;

an included angle between the main axis direction and the horizontal direction of the first half wave plate (2) is 0 degree, the first half wave plate is attached to a light beam transmission interface of the first non-polarization beam splitter (1) and used for enabling a vertical polarization component of the second signal light to delay a phase pi relative to a horizontal polarization component;

the polarization beam splitter (3) is used for carrying out polarization beam splitting on the first signal light to generate a first polarization component and a second polarization component; and a polarization beam splitter for polarization splitting the second signal light to generate a third polarization component and a fourth polarization component;

the first magneto-optical polarization rotation module (4) is used for rotating the polarization of the second polarization component and the third polarization component by 90 degrees, and is used for enabling the polarization of the second interference component, the third interference component, the fifth interference component and the eighth interference component to be unchanged when passing through;

the second magneto-optical polarization rotation module (5) is used for enabling the polarization of the first polarization component and the fourth polarization component to be unchanged when the first polarization component and the fourth polarization component pass through, and is used for enabling the polarization of the first interference component, the fourth interference component, the sixth interference component and the seventh interference component to be rotated by 90 degrees;

the first beam shifter (6) and the second beam shifter (7) are used for enabling the horizontal polarized light signals passing through the first beam shifter to pass through linearly and enabling the vertical polarized light signals to exit after being shifted;

the polarization beam splitter (3) is also used for carrying out polarization beam combination on the first interference component and the third interference component to generate first interference output light; polarizing and beam combining the second interference component and the fourth interference component to generate second interference output light; polarizing and combining the fifth interference component and the seventh interference component to generate third interference output light; and carrying out polarization beam combination on the sixth interference component and the eighth interference component to generate fourth interference output light.

2. The four-in-one spatial light retardation self interferometer according to claim 1, wherein said set of mirrors comprises a first mirror (8), a second mirror (9), a third mirror (10), a fourth mirror (11), a fifth mirror (12) and a sixth mirror (13) having reflecting surfaces all parallel to the polarizing beam splitting interface of the polarizing beam splitter (3),

the first reflector (8) is positioned above a light beam reflecting interface of the first non-polarization beam splitter (1) and used for reflecting the first signal light to enable the first signal light to vertically enter the lower part of the center of the first interface of the polarization beam splitter (3);

the second reflecting mirror (9) is positioned at the right side of the light beam transmission interface of the first non-polarization beam splitter (1) and is used for reflecting the second signal light to enable the second signal light to be vertically incident to the center of the second interface of the polarization beam splitter (3);

the third reflector (10) is positioned at the right side of the second beam deflector (7) and corresponds to the lower central part of the third interface of the polarization beam splitter (3) and is used for reflecting the first polarization component, the fourth interference component and the sixth interference component;

the fourth reflector (11) is positioned above the first beam deflector (6) and corresponds to the left part of the center of the fourth interface of the polarization beam splitter (3) and is used for reflecting the second polarization component, the third polarization component, the second interference component and the eighth interference component;

the fifth reflector (12) is positioned above the first magneto-optical polarization rotation module (4), corresponds to the right part of the center of a fourth interface of the polarization beam splitter (3), and is used for reflecting a third interference component and a fifth interference component;

the sixth reflector (13) is positioned at the right side of the second magneto-optical polarization rotation module (5), corresponds to the upper part of the center of the third interface of the polarization beam splitter (3), and is used for reflecting the first interference component and the seventh interference component;

the length of the first beam shifter (6) is less than the side length of the polarization beam splitter (3), and one end of the first beam shifter is aligned with a first interface of the polarization beam splitter, so that the second polarization component and the second interference component can pass through the first beam shifter in a straight line, and the third polarization component and the eighth interference component can be shifted and emitted;

the second beam deflector (7) and the first beam deflector (6) are equal in length, and one end of the second beam deflector is aligned with the second interface of the polarization beam splitter (3) and used for enabling the first polarization component and the fourth interference component to pass through in a straight line and enabling the fourth polarization component and the sixth interference component to be deflected and emitted.

3. The four-in-one spatial light delay self interferometer according to claim 1, wherein the mirror group comprises a first mirror (8), a second mirror (9), a third mirror (10), a fourth mirror (11), a fifth mirror (12) and a sixth mirror (13) with their reflective surfaces all parallel to the polarizing beam splitting interface of the polarizing beam splitter (3),

the first reflector (8) is positioned above the light beam reflection interface of the first non-polarization beam splitter (1) and used for reflecting the first signal light to enable the first signal light to vertically enter the upper part of the center of the first interface of the polarization beam splitter (3);

the second reflecting mirror (9) is positioned on the right side of the light beam transmission interface of the first non-polarization beam splitter (1) and is used for reflecting the second signal light to enable the second signal light to vertically enter the left part of the center of the second interface of the polarization beam splitter (3);

the third reflector (10) is positioned at the right side of the second beam deflector (7) and corresponds to the center of a third interface of the polarization beam splitter (3) and is used for reflecting a fourth polarization component, a first interference component and a sixth interference component;

the fourth reflector (11) is positioned above the first beam deflector (6) and corresponds to the center of a fourth interface of the polarization beam splitter (3) and is used for reflecting a third polarization component, a third interference component and an eighth interference component;

the fifth reflector (12) is positioned above the first beam deflector (6) and corresponds to the right part of the center of the fourth interface of the polarization beam splitter (3) and is used for reflecting the second polarization component, the second interference component and the fifth interference component;

the sixth reflecting mirror (13) is positioned at the right side of the second beam deflector (7) and corresponds to the upper part of the center of the third interface of the polarization beam splitter (3) and is used for reflecting the first polarization component, the fourth interference component and the seventh interference component;

the length of the first beam shifter (6) is equal to the side length of the polarization beam splitter (3), and the first beam shifter is used for enabling the second polarization component, the second interference component and the third interference component to pass through linearly and enabling the third polarization component, the fifth interference component and the eighth interference component to be shifted and emitted;

the second beam deflector (7) has the same length as the first beam deflector (6) and is used for enabling the first polarization component, the first interference component and the fourth interference component to pass through linearly and enabling the fourth polarization component, the sixth interference component and the seventh interference component to be deflected and emitted.

4. The four-in-one spatial light retardation self-interferometer according to claim 2, wherein the first magneto-optical polarization rotation module (4) comprises a second half-wave plate (4-1) and a first faraday rotation plate (4-2) attached to each other, wherein the second half-wave plate (4-1) has a principal axis direction having an angle of 22.5 ° with the horizontal direction, and the side thereof not attached to the first faraday rotation plate (4-2) is attached to the fourth interface of the polarization beam splitter (3); the polarization rotation angle of the first Faraday rotation plate (4-2) is 45 degrees, and one side, which is not attached to the second half-wave plate (4-1), of the first Faraday rotation plate is attached to the first beam shifter (6);

the second magneto-optical polarization rotation module (5) also comprises a second half-wave plate (4-1) and a first Faraday optical rotation plate (4-2) which are attached to each other, wherein an included angle between the main shaft direction of the second half-wave plate (4-1) and the horizontal direction is 22.5 degrees, and one side, which is not attached to the second half-wave plate (4-1), of the first Faraday optical rotation plate (4-2) is attached to a third interface of the polarization beam splitter (3); and one side of the second half-wave plate (4-1), which is not attached to the first Faraday rotation plate (4-2), is attached to a second beam shifter (7).

5. The four-in-one spatial light retardation self-interferometer according to claim 3, wherein the first magneto-optical polarization rotation module (4) comprises a second Faraday rotation plate (4-3) and a third half-wave plate (4-4) attached to each other, where the polarization rotation angle of the second Faraday rotation plate (4-3) is 45 ° and the side not attached to the third half-wave plate (4-4) is attached to the fourth interface of the polarization beam splitter (3); the included angle between the main shaft direction of the third half-wave plate (4-4) and the horizontal direction is-22.5 degrees, and one side of the third half-wave plate, which is not attached to the second Faraday optical rotation plate (4-3), is attached to the first beam shifter (6);

the second magneto-optical polarization rotation module (5) also comprises a second Faraday optical rotation plate (4-3) and a third half-wave plate (4-4) which are attached to each other, wherein one side, which is not attached to the second Faraday optical rotation plate (4-3), of the third half-wave plate (4-4) is attached to a third interface of the polarization beam splitter (3); an included angle between the main axis direction of the third half-wave plate (4-4) and the horizontal direction is-22.5 degrees, and one side, which is not jointed with the third half-wave plate (4-4), of the second Faraday optical rotation plate (4-3) is jointed with the second beam shifter (7).

6. The four-in-one spatial light retardation self-interferometer of claim 1, 2, 3, 4 or 5, wherein the 2*2 unequal arm interferometer comprises a second non-polarizing beam splitter (14), a first right angle prism (15), a second right angle prism (16), a quarter wave plate (17),

the beam splitting interface of the second non-polarization beam splitter (14) and the polarization beam splitting interface of the polarization beam splitter (3) are in the same plane, and the fourth interface and the third interface are respectively parallel to the inclined planes of the first right-angle prism (15) and the second right-angle prism (16), the distances between the fourth interface and the third interface are unequal, and the distance difference is half of the arm length difference of the 2*2 unequal-arm interferometer;

the quarter wave plate (17) is located at the lower side position between the second right-angle prism (16) and the light beam reflection interface of the second non-polarization beam splitter (14) and used for enabling the phase of the vertically polarized light signal passing through the quarter wave plate to be increased by pi/2 and the phase of the horizontally polarized light signal to be unchanged.

7. The four-in-one spatial light retardation self-interferometer according to claim 6, wherein the second right-angle prism (16) is located on a one-dimensional displacement stage, and the axis direction of the one-dimensional displacement stage is perpendicular to the inclined plane of the second right-angle prism (16) for adjusting the arm length difference of the 2*2 unequal arm interferometer.