CN114166201B - An Integrated Polarization Suppressing Fiber Resonator - Google Patents

Abstract

The invention provides an integrated polarization suppression fiber resonant cavity based on spatial coupling, which comprises a base (30), and a first input optical channel, a second input optical channel, a circulating optical channel, a first output optical channel and a second output optical channel which are integrated on the base (30). The invention integrates all optical parts to effectively reduce the volume of the optical fiber resonant cavity, can well inhibit the polarization fluctuation noise in the resonant cavity by the special arrangement mode of the optical fiber, the polarizer and other components, and is suitable for novel optical fibers, especially hollow optical fibers.

Description

An Integrated Polarization Suppressing Fiber Resonator

technical field

The invention belongs to the field of optical fiber resonant cavities, in particular to an integrated polarization-suppressing optical fiber resonant cavity.

Background technique

Resonator Fiber Optic Gyro (RFOG) is an angular rate sensor that obtains angular rate information by detecting clockwise and counterclockwise beam frequencies in a fiber resonator based on the Sagnac effect. The resonant fiber optic gyroscope combines the advantages of the resonance detection of the laser gyroscope and the multi-turn optical path of the interferometric fiber optic gyroscope, and is expected to achieve high-precision measurement with a shorter fiber length. An important direction for the development of gyroscopes.

The main sensitive component in the resonant fiber optic gyroscope is the fiber optic resonator, and its performance directly affects the accuracy of the gyroscope. When the gyroscope is working, there are two orthogonal intrinsic polarizations (Eigenstate of polarization, ESOP) in the fiber resonator. However, affected by the external environment, there will be fluctuations and crosstalk between the two polarization states, resulting in superposition and interference effects, causing asymmetry and fluctuations in the resonance signal. The noise generated by the polarization fluctuation in the output of the gyro is the polarization fluctuation noise. Polarization fluctuation noise is one of the important noise sources in the resonant fiber optic gyro system.

At present, fiber resonators are mostly constructed by high-temperature fusion splicing of solid-core polarization-maintaining fiber couplers. Since the core of polarization-maintaining fibers is quartz glass, it is easily affected by ambient temperature and has high optical noise, which restricts the further development of fiber resonators. As a new type of optical fiber, hollow-core photonic crystal fiber is superior to existing optical fibers in terms of temperature sensitivity and multiple optical properties. At the same time, the smaller bending radius is also conducive to the miniaturization of fiber resonators. There are air holes in the fiber of the hollow core fiber. High temperature fusion splicing will easily lead to the collapse of the air holes and cause a large loss, which is not suitable for traditional splicing methods. The lack of corresponding ideal couplers limits the use of photonic crystal fibers on fiber resonators.

To suppress the influence of polarization fluctuation noise on the gyroscope, methods such as controlling the alignment error during welding or adding an online polarizer in the resonant cavity are usually used. The former requires strict control of the alignment angle with high precision, while the latter is not conducive to miniaturization when spliced with optical fiber devices, and is not suitable for hollow-core photonic crystal fibers. At the same time, due to the fragility of the fiber at the fusion point, the large minimum bending radius also limits the miniaturization of the fiber resonator. Therefore, the current fiber resonator cannot meet the miniaturization and single polarization performance well.

Contents of the invention

The purpose of the present invention is to provide an integrated polarization-suppressing fiber resonator based on spatial coupling. While integrating all optical components to effectively reduce the volume of the fiber resonator, the special arrangement of components such as optical fibers and polarizers can be well The polarization fluctuation noise in the resonator can be suppressed, and the scheme is suitable for new types of optical fibers, especially hollow-core optical fibers.

The technical solution of the present invention: provide an integrated polarization-suppressing fiber resonator, the fiber resonator includes a base 30 and a first input optical channel, a second input optical channel, a circulation optical channel, a first output optical channel, a second output optical channel;

The first input optical channel includes a first emission fiber 1, a first coupling lens 5, and a first polarizer 13; the second input optical channel includes a second input optical fiber 2, an eighth coupling lens 12, and a first polarizer 13;

The circulating optical channel includes the first beam splitter 15, the second coupling lens 6, the first fiber upper end 21 and the first fiber lower end 22 of the first optical fiber 19, the third coupling lens 7, the second beam splitter 16, The fourth polarizer 26, the third beam splitter 17, the sixth coupling lens 10, the second fiber lower end 23 and the second fiber upper end 24 of the second optical fiber 20, the seventh coupling lens 11, the fourth beam splitter 18 and The third polarizer 25;

The first output optical channel includes the second polarizer 14, the fourth coupling lens 8 and the first receiving optical fiber 3 arranged in sequence; the second output optical channel includes the second polarizer 14, the fifth coupling lens 9 and the second optical fiber arranged in sequence. The second receiving optical fiber 4;

The first light b1 passes through the first input light channel, is reflected into the circular light channel by the first beam splitter 15, and forms the first circular light b10 after multiple cycles, and the first circular light b10 is reflected by the second beam splitter 16 into the circular light channel. The first output optical channel output;

The second light b2 passes through the second input light channel, is reflected into the circular light channel by the fourth beam splitter 18, and forms the second circular light b20 after multiple cycles, and the second circular light b20 is reflected by the third beam splitter 17 into the circular light channel. The second output optical channel outputs.

Optionally, the polarization directions of the first polarizer 13 and the third polarizer 25 are the same, both are the first polarization direction Z1; the polarization directions of the second polarizer 14 and the fourth polarizer 26 are the same, both are is the second polarization direction Z2; the first polarization direction Z1 and the second polarization direction Z2 are both orthogonal.

Optionally, both the first optical fiber 19 and the second optical fiber 20 include a first polarization axis P1 and a second polarization axis P2;

The first polarization axis P1 of the upper end 21 of the first optical fiber is the same as the first polarization direction Z1, and the first polarization axis P1 of the lower end 22 of the first optical fiber is the same as the second polarization direction Z2;

The second polarization axis P2 of the upper end 24 of the second optical fiber is the same as the first polarization direction Z1, and the second polarization axis P2 of the lower end 23 of the second optical fiber is the same as the second polarization direction Z2;

The first polarization axis P1 of the upper end 21 of the first optical fiber is aligned with the second polarization axis P2 of the upper end 24 of the second optical fiber;

The first polarization axis P1 of the first fiber lower end 22 is aligned with the second polarization axis P2 of the second fiber lower end 23 .

Optionally, the first polarizer 13 is selected from a polarizer, and the third polarizer 25 is selected from a polarizer or a polarization splitter prism.

Optionally, the first polarizer 13 , the second polarizer 14 , the third polarizer 25 , and the fourth polarizer 26 are all placed at an angle of 8° to the optical path to reduce backscattered light.

Optionally, the length difference between the first optical fiber 19 and the second optical fiber 20 is less than 3/1000 of the length of the first optical fiber 19 or the second optical fiber 20 .

Optionally, the first optical fiber 19 and the second optical fiber 20 are wound clockwise or counterclockwise multiple times to form a ring.

Optionally, the first beam splitter 15 and the second beam splitter 16 are tilted by 45° relative to the first light ray b1; the fourth beam splitter 18 and the third beam splitter 17 are inclined relative to the second light b2 Inclined at 45°.

Optionally, the base 30 is a silicon-based semiconductor chip.

The advantages of the present invention: the present invention adopts the principle of space optics to realize the function of the optical fiber resonator, avoids the traditional welding method, and is suitable for new optical fibers, especially hollow-core optical fibers; the present invention adopts specially set component parameters and optical path structure to realize a A reciprocal optical path for polarization fluctuation suppression is beneficial to reduce gyro polarization fluctuation noise and suppress gyro common-mode error; the invention integrates traditional resonant cavity discrete components on the substrate, which is beneficial to packaging and miniaturization; for reducing the fiber resonant cavity It is of great significance to suppress the noise of the fiber resonator and improve the signal-to-noise ratio of the gyroscope.

The optical fiber resonator has polarization fluctuation suppression characteristics, and the sub-resonance peak (dashed line) corresponding to the sub-polarization state in the spectrum curve is far away from the main resonant peak (solid line) corresponding to the main polarization state, and the fluctuation between the frequencies of the primary and sub-resonance peaks is suppressed and the amplitude of the sub-polarization peak, so that the polarization fluctuation noise caused by the sub-harmonic peak can be reduced.

Description of drawings:

Fig. 1 is a schematic diagram of the integrated polarization-suppressing fiber resonator of the present invention;

Fig. 2 is the structural representation of the first optical fiber upper port (left figure) and the second optical fiber upper port (right figure) of the present invention;

Fig. 3 is a structural schematic diagram of a first polarizer (upper figure) and a second polarizer (lower figure);

FIG. 4 is the spectrum distribution of the first light b1 and the second light b2 received by the first receiving optical fiber 3 and the second receiving optical fiber 4 under different input light frequencies.

Among them, 1-first transmitting fiber, 2-second transmitting fiber, 3-first receiving fiber, 4-second receiving fiber, 5-first coupling lens, 6-second coupling lens, 7-third coupling lens , 8-fourth coupling lens, 9-fifth coupling lens, 10-sixth coupling lens, 11-seventh coupling lens, 12-eighth coupling lens, 13-first polarizer, 14-second polarizer , 15-first beam splitter, 16-second beam splitter, 17-third beam splitter, 18-fourth beam splitter, 19-first fiber, 20-second fiber, 21-first fiber Upper end, 22-the lower end of the first optical fiber, 23-the upper end of the second optical fiber, 24-the lower end of the second optical fiber, 25-the third polarizer, 26-the fourth polarizer, 30-base, b1-the first light, b2-second light, b10-first cycle light, b20-second cycle light.

Detailed ways:

The present invention will be further described below by accompanying drawing:

Example 1

Referring to FIG. 1 , this embodiment provides a miniaturized single-polarization fiber resonator. The integrated polarization-suppressing fiber resonator of the present invention includes: a first optical fiber 19, a second optical fiber 20 and a base 30, and a first emitting optical fiber 1, a second emitting optical fiber 2, a first receiving optical fiber 3, a first emitting optical fiber 3, and a base are arranged on the base Two receiving optical fibers 4, the first coupling lens 5, the second coupling lens 6, the third coupling lens 7, the fourth coupling lens 8, the fifth coupling lens 9, the sixth coupling lens 10, the seventh coupling lens 11, the eighth coupling lens Lens 12, first polarizer 13, second polarizer 14, first beam splitter 15, second beam splitter 16, third beam splitter 17, fourth beam splitter 18, first optical fiber upper end 21, The first optical fiber lower end 22, the second optical fiber lower end 23, the second optical fiber upper end 24, the third polarizer 25, the fourth polarizer 26, the first light b1, the second light b2, the first circulating light b10, the second Loop light b20.

The first optical fiber 19 and the second optical fiber 20 are wound clockwise or counterclockwise multiple times to form a ring, and both ends are fixed on the base 30, respectively the upper end 21 of the first optical fiber, the lower end 22 of the first optical fiber, and the upper end 23 of the second optical fiber. , the lower end 24 of the second optical fiber.

The first light b1 passes through the first input light channel, is reflected into the circular light channel by the first beam splitter 15, and forms the first circular light b10 after multiple cycles, and the first circular light b10 is reflected by the second beam splitter 16 into the circular light channel. The first output optical channel outputs.

In this embodiment, the specific optical transmission path of the first light b1 is as follows: the first input optical fiber 1 emits the first light b1 through the first coupling lens 5 in turn, the first polarizer 6 reaches the first beam splitter 15, and is reflected by the first light beam b1. Two coupling lenses 6 are coupled into the upper end 21 of the first optical fiber, and are emitted from the lower end 22 of the first optical fiber after being transmitted through the first optical fiber 19, passing through the third coupling lens 7, the second beam splitter 16, the fourth polarizer 26, The third beam splitter 17 is coupled into the lower end 23 of the second optical fiber by the sixth coupling lens 10, after being transmitted through the second optical fiber 20 and exiting from the upper end 24 of the second optical fiber, it passes through the seventh coupling lens 11 and the fourth beam splitting mirror in turn. The mirror 18 and the third polarizer 25 reach the first beam splitter mirror 15, and are coupled into the upper end 21 of the first optical fiber by the second coupling lens 6 again, so that the first circulating light b10 is formed after multiple cycles. Part of the recycled light is reflected by the second beam splitter 16 , passes through the second polarizer 14 , and is combined into the first receiving optical fiber 3 by the fourth coupling lens 8 .

The second light b2 passes through the second input optical channel, is reflected into the circular optical channel through the fourth beam splitter (18), forms the second circular light b20 after multiple cycles, and the second circular light b20 passes through the third beam splitter ( 17) Reflected into the second output optical channel for output.

In this embodiment, the specific optical transmission path of the second light b2 is as follows: the second light b2 emitted by the second input optical fiber 2 passes through the eighth coupling lens 12 sequentially, the first polarizer 6 reaches the fourth beam splitter 18, and is reflected by the second light b2. The seven coupling lenses 11 are coupled into the second optical fiber upper end 24, and after being transmitted through the second optical fiber 20, the output is emitted from the second optical fiber lower end 23, passing through the sixth coupling lens 10, the third beam splitter 17, the fourth polarizer 26, The second beam splitter 16 is coupled into the lower end 22 of the first optical fiber by the third coupling lens 7, after being transmitted through the first optical fiber 19 and exiting from the upper end 21 of the first optical fiber, it passes through the second coupling lens 6 and the first beam splitting mirror in turn. The mirror 15 and the second polarizer 25 reach the fourth beam splitter mirror 18, and are coupled into the upper end 24 of the second optical fiber by the seventh coupling lens 11 again, so as to form the second circulating light b20 after multiple cycles. Part of the recycled light is reflected by the third beam splitter 17 , passes through the second polarizer 14 , and is coupled into the second receiving optical fiber 4 by the fifth coupler 9 .

The polarizing directions of the first polarizer 13 and the third polarizer 25 are the same as the first polarizing direction Z1, and the polarizing directions of the second polarizer 14 and the fourth polarizer 26 are the same as the second polarizing direction In the direction Z2, the first polarization direction Z1 and the second polarization direction Z2 are perpendicular to each other. The first polarizer 13 is placed between the first coupling lens 5, the eighth coupling lens 12, the first beam splitter 15, and the fourth beam splitter 18; the second polarizer 14 is placed between the fourth coupling lens 8, the second Five coupling lenses 9 and the second beam splitter 16, between the third beam splitter 17; the third polarizer 25 is placed between the first beam splitter 15 and the fourth beam splitter 18; the fourth polarizer Placed between the second beam splitter 16 and the third beam splitter 17; the first polarizer 13, the second polarizer 14, the third polarizer 25, the fourth polarizer 26 and the optical path 8 ° Positioned at an angle to reduce backscattered light.

The first polarizer 13 is used to prevent the light component of the second polarization direction Z2 in the first light b1 and the second light b2 emitted by the first emitting optical fiber 1 and the second emitting optical fiber 2 from entering the second coupling lens 6 and the seventh coupling lens 11, thereby reducing the secondary polarization state in the first circulating light b10 and the second circulating light b20; the second polarizer 14 is used to suppress the The light component of the first polarization direction Z1 in the received first light b1 and second light b2 enters the second coupling lens 6 and the seventh coupling lens 11, thereby suppressing the The effect of the secondary polarization state on the detected signal.

The third polarizer is used to suppress the light component of the second polarization direction Z2 between the first beam splitter 15 and the fourth beam splitter 18; the fourth polarizer is used to suppress the second beam splitter 16 and the second beam splitter 18 The light component of the first polarization direction Z1 between the three beam splitters 17; finally suppress the secondary polarization state in the first recirculating light b10 and the second recirculating light b20, thereby reducing the influence of the secondary polarization state on the detection signal.

Due to the anisotropy, the first optical fiber 19 and the second optical fiber 20 have the function of maintaining the polarization state, and there are two polarization axes in the cross section, which are the first polarization axis P1 and the second polarization axis P2. Wherein the first polarization axis P1 of the first optical fiber upper end 21 is the same as the first polarization direction Z1, the first polarization axis P1 of the first optical fiber lower end 22 is the same as the second polarization direction Z2; the second polarization axis P2 of the second optical fiber upper end 24 Same as the first polarization direction Z1, the second polarization axis P2 of the second optical fiber lower end 23 is the same as the second polarization direction Z2. At this time, the first polarization axis P1 of the upper end 21 of the first optical fiber is aligned with the second polarization axis P2 of the upper end 24 of the second optical fiber, and the first polarization axis P1 of the lower end 22 of the first optical fiber is aligned with the second polarization of the upper end 24 of the second optical fiber Axis P2. The lengths of the first optical fiber 19 and the second optical fiber 20 should be kept as the same as possible. Taking an optical fiber of 10 m as an example, the length difference is less than 3 cm, so that the secondary polarization states in the first circulating light b10 and the second circulating light b20 correspond to resonance The peak is far away from the resonance peak corresponding to the main polarization state, and the polarization fluctuation noise formed by the drift between the primary and secondary polarization state resonance peaks caused by the fluctuation of the external environment is suppressed.

The first beam splitter 15 and the second beam splitter 16 are placed at an inclination of 45° relative to the first light b1, reflect the first light b1 into the second coupling lens 6, and partially reflect the first recycled light b10 into the fourth Coupling lens 8; The fourth beam splitter 18 and the third beam splitter 17 are inclined at 45° relative to the second light b2, and the second light b2 is reflected into the seventh coupling lens 11, and the second recycled light b20 Part of it is reflected into the fifth coupling lens 9; the coupling of the first light b1 and the second light b2 into and out of the resonant cavity is realized.

The base 30 is processed by silicon-based semiconductor technology, has the characteristics of integration and miniaturization, and is suitable for mass production in the future. In this embodiment, the reflection mirror and the polarizer can also be etched or directly grown on the silicon base, and then the function can be realized by coating, so as to realize the integration of the resonant cavity and enhance the stability of the resonant cavity.

Further, the first beam splitter 15 and the second beam splitter 16 include a partially reflective coating surface and a high transmittance coating surface. The partially reflective coating surfaces of the first beam splitter 15 and the second beam splitter 16 are located on opposite sides; the high transmittance coating surfaces of the first beam splitter 15 and the second beam splitter 16 are located on opposite sides sides. The reflectance of the reflective coating surface is 1%-10%. The coating conditions of the fourth beam splitter 18 and the third beam splitter 17 are similar to those of the first beam splitter 15 and the second beam splitter 16 .

As shown in FIG. 2 , a schematic structural diagram of the upper port of the first optical fiber and the upper port of the second optical fiber is given. Due to the anisotropy of the first optical fiber 19 and the second optical fiber 20 , there are two polarization axes respectively the first polarization axis Z1 and the second polarization axis Z2 , and the transmission of light along the axial direction has the characteristic of keeping the polarization unchanged.

As shown in FIG. 3 , a schematic structural diagram of the first polarizer 13 and the second polarizer 14 is given. The polarization direction of the first polarizer is the first polarization direction P1, and the polarization direction of the second polarizer is the second polarization direction P2. When the beam passes through the first polarizer, the light component in the second polarization direction is filtered out, which reduces the amplitude of the secondary polarization state component in the circulating light; when the beam passes through the second polarizer, the light component in the first polarization direction is filtered out , which reduces the influence of the secondary polarization state component in the circulating light on the main polarization state during detection.

As shown in FIG. 4 , the spectral distributions of the first light b1 and the second light b2 received by the first receiving optical fiber 3 and the second receiving optical fiber 4 under different input light frequencies are given. The optical fiber resonator has polarization fluctuation suppression characteristics, and the sub-resonance peak (dashed line) corresponding to the sub-polarization state in the spectrum curve is far away from the main resonant peak (solid line) corresponding to the main polarization state, and the fluctuation between the frequencies of the primary and sub-resonance peaks is suppressed and the amplitude of the sub-polarization peak, so that the polarization fluctuation noise caused by the sub-harmonic peak can be reduced.

In summary, the present invention adopts the principle of space optics to realize the function of the fiber resonator, avoids the traditional fusion splicing method, and is suitable for new optical fibers, especially hollow-core optical fibers; the present invention adopts specially set component parameters and optical path structure to realize a The reciprocal optical path of polarization fluctuation suppression is beneficial to reduce the polarization fluctuation noise of the gyroscope and suppress the common mode error of the gyroscope; the invention integrates the traditional resonant cavity discrete components on the substrate, which is beneficial to packaging and miniaturization; for reducing the optical fiber resonant cavity It is of great significance to suppress the noise of the fiber resonator and improve the signal-to-noise ratio of the gyroscope.

Claims (8)

1. An integrated polarization-suppressing fiber resonator, characterized in that, said fiber resonator comprises a base (30) and a first input optical channel integrated on the base (30), a second input optical channel, a circulation an optical channel, a first output optical channel, and a second output optical channel; The first input optical channel includes a first emission fiber (1), a first coupling lens (5) and a first polarizer (13); the second input optical channel includes a second input optical fiber (2), an eighth coupling lens (12) ) and the first polarizer (13); The circulating optical channel includes a first beam splitter mirror (15), a second coupling lens (6), a first optical fiber upper end (21) and a first optical fiber lower end (22) of the first optical fiber (19) arranged in sequence, a third coupling lens Lens (7), the second beam splitter (16), the fourth polarizer (26), the third beam splitter (17), the sixth coupling lens (10), the second optical fiber of the second optical fiber (20) The lower end (23) and the second optical fiber upper end (24), the seventh coupling lens (11), the fourth beam splitter (18) and the third polarizer (25); The first output optical channel includes a second polarizer (14), a fourth coupling lens (8) and a first receiving optical fiber (3) arranged in sequence; the second output optical channel includes a second polarizer (14) arranged in sequence ), the fifth coupling lens (9) and the second receiving optical fiber (4); The first light b1 passes through the first input light channel, is reflected into the circulation light channel by the first beam splitter (15), forms the first cycle light b10 after multiple cycles, and the first cycle light b10 passes through the second beam splitter ( 16) reflected into the first output optical channel output; The second light b2 passes through the second input optical channel, is reflected into the circular optical channel through the fourth beam splitter (18), forms the second circular light b20 after multiple cycles, and the second circular light b20 passes through the third beam splitter ( 17) reflected into the second output optical channel output; Wherein, the polarizing directions of the first polarizer (13) and the third polarizer (25) are the same, both being the first polarizing direction Z1; the polarizing directions of the second polarizer 14 and the fourth polarizer 26 are the same , are both the second polarization direction Z2; the first polarization direction Z1 and the second polarization direction Z2 are both orthogonal. 2. The integrated polarization-suppressing fiber resonator according to claim 1, wherein the first optical fiber (19) and the second optical fiber (20) both comprise a first polarization axis P1 and a second polarization axis P2; The first polarization axis P1 of the upper end (21) of the first optical fiber is the same as the first polarization direction Z1, and the first polarization axis P1 of the lower end (22) of the first optical fiber is the same as the second polarization direction Z2; The second polarization axis P2 of the second fiber upper end (24) is the same as the first polarization direction Z1, and the second polarization axis P2 of the second fiber lower end (23) is the same as the second polarization direction Z2; The first polarization axis P1 of the first optical fiber upper end (21) is aligned with the second polarization axis P2 of the second optical fiber upper end (24); The first polarization axis P1 of the lower end (22) of the first optical fiber is aligned with the second polarization axis P2 of the lower end (23) of the second optical fiber. 3. The integrated polarization-suppressing fiber resonator according to claim 1, wherein the first polarizer (13) is a polarizer, and the third polarizer (25) is a polarizer or a polarization beam splitter. 4. The integrated polarization-suppressing fiber resonator according to claim 1, characterized in that, the first polarizer (13), the second polarizer (14), the third polarizer (25), the first polarizer The four polarizers (26) are placed at an angle of 8° to the optical path to reduce backscattered light. 5. The integrated polarization-suppressing fiber resonator according to claim 1, characterized in that the length difference between the first optical fiber (19) and the second optical fiber (20) is smaller than that of the first optical fiber (19) or the second optical fiber (19) Three thousandths of the length of the optical fiber (20). 6. The integrated polarization-suppressing fiber resonator according to claim 1, characterized in that, the first optical fiber (19) and the second optical fiber (20) are wound clockwise or counterclockwise multiple times to form a ring. 7. The integrated polarization-suppressing fiber resonator according to claim 1, characterized in that, the first beam splitter (15) and the second beam splitter (16) are inclined at 45° with respect to the first light b1; The fourth beam splitter (18) and the third beam splitter (17) are placed obliquely at 45° relative to the second light b2. 8. The integrated polarization-suppressing fiber resonator according to claim 1, characterized in that the base (30) is a silicon-based semiconductor chip.

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