CN116931297A

CN116931297A - Optical resonant cavity and optical filter

Info

Publication number: CN116931297A
Application number: CN202210371893.5A
Authority: CN
Inventors: 昌钟璨; 万助军; 欧阳奎
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-04-11
Filing date: 2022-04-11
Publication date: 2023-10-24

Abstract

The application provides an optical resonant cavity and an optical filter, which relate to the technical field of optical communication, and have improved filtering effect; the first electrode and the second electrode are respectively arranged at two sides of the electro-optic crystal along the propagation direction of the electro-optic crystal; the first electrode and the second electrode apply an electric field to the electro-optic crystal, the electric field is used for adjusting the refractive index of the electro-optic crystal, and the electric field has a component parallel to the propagation direction; a first reflective film and a second reflective film, wherein the first reflective film is disposed on a side of the first electrode away from the electro-optic crystal, and the second reflective film is disposed on a side of the second electrode away from the electro-optic crystal; and a temperature control structure, wherein the temperature control structure applies a temperature to the electro-optic crystal to adjust the refractive index of the electro-optic crystal.

Description

Optical resonant cavity and optical filter

Technical Field

The present disclosure relates to the field of optical communications, and in particular, to an optical resonant cavity and an optical filter.

Background

The optical fiber transmission uses light as a carrier wave, and uses an optical fiber as a transmission medium to transmit signals. Among them, a backbone network is a high-speed network for connecting a plurality of areas or regions, and in the backbone network, optical fiber transmission is generally used. With the development of communication technology and the increase of data demand, reconfigurable optical add-drop multiplexers (ROADMs) in backbone networks need to sink to metropolitan area networks to achieve the purpose of network upgrade. In general, the reconfigurable optical add/drop multiplexer needs to use an optical performance monitor (optical performance monitor, OPM) to detect the signal-to-noise ratio and power of the optical signal transmitted by the optical fiber, so as to ensure that the crosstalk level and the bit error rate of the optical signal in the optical fiber transmission are controllable.

The core component of the optical performance monitor is an optical filter (tunable optical filter, TOF), most of which can achieve the purpose of filtering out light rays with different wavelengths by tuning certain parameters in the optical filter, however, the wavelength tuning range of the existing optical filter is limited, so that the filtering effect is limited.

Disclosure of Invention

The embodiment of the application provides an optical resonant cavity and an optical filter, which can improve the filtering effect of the optical resonant cavity.

In order to achieve the above purpose, the embodiment of the application adopts the following technical scheme:

in a first aspect, there is provided an optical resonator comprising: an electro-optic crystal; the first electrode and the second electrode are respectively arranged at two sides of the electro-optic crystal along the propagation direction of the electro-optic crystal; the first electrode and the second electrode are used for applying an electric field to the electro-optic crystal, the electric field is used for adjusting the refractive index of the electro-optic crystal, and the electric field has a component parallel to the propagation direction; a first reflective film and a second reflective film, wherein the first reflective film is disposed on a side of the first electrode away from the electro-optic crystal, and the second reflective film is disposed on a side of the second electrode away from the electro-optic crystal; a temperature control structure, wherein the temperature control structure applies a temperature to the electro-optic crystal to adjust a refractive index of the electro-optic crystal; a first reflective film for transmitting an input light in a propagation direction, the transmitted light being transmitted to the electro-optical crystal through the first electrode; an electro-optical crystal for transmitting light transmitted by the first reflective film to the second reflective film through the second electrode at a predetermined refractive index under the action of temperature and an electric field; the second reflecting film is used for outputting light rays with a preset wavelength in the light rays transmitted by the electro-optical crystal and reflecting the light rays with other wavelengths except the preset wavelength to the electro-optical crystal through the second electrode; the electro-optical crystal is also used for transmitting the light reflected by the second reflecting film to the first reflecting film through the first electrode at a preset refractive index; the first reflecting film is also used for reflecting the light transmitted by the electro-optical crystal to the electro-optical crystal through the first electrode. In the optical resonator described above, by providing the first electrode and the second electrode on both sides of the electro-optical crystal along the propagation direction of the electro-optical crystal, respectively, when a driving voltage is applied to the first electrode and the second electrode, an electric field is formed in the electro-optical crystal, and there is a component parallel to the propagation direction of the electric field, and the refractive index of the electro-optical crystal is changed by the electric field. And a first reflecting film is arranged on one side of the first electrode far away from the electro-optical crystal, and a second reflecting film is arranged on one side of the second electrode far away from the electro-optical crystal, so that the first reflecting film, the second reflecting film and the electro-optical crystal filter input light. And a temperature control structure is also arranged on the electro-optic crystal, the temperature control structure is connected to a power supply to form a current loop, and resistance heat is generated under the action of the current loop, and the resistance heat forms the temperature transmitted to the electro-optic crystal. The refractive index of the electro-optic crystal will become a predetermined refractive index under the combined action of temperature and electric field. Then, when the electric field intensity and the temperature in the electro-optic crystal are different, the input light transmitted by the first reflective film in the propagation direction is transmitted to the electro-optic crystal through the first electrode, and the electro-optic crystal is transmitted to the second reflective film through the second electrode at a predetermined refractive index corresponding to the electric field intensity and the temperature in the electro-optic crystal. The second reflecting film outputs light rays with a preset wavelength in the light rays transmitted through the electro-optical crystal, namely, the light rays with the preset wavelength are transmitted out of the second reflecting film, and the light rays with other wavelengths except the preset wavelength are reflected back to the electro-optical crystal through the second electrode, so that the electro-optical crystal transmits the light rays reflected by the second reflecting film to the first reflecting film through the first electrode with a preset refractive index, and the first reflecting film is further used for reflecting the light rays transmitted by the electro-optical crystal to the electro-optical crystal through the first electrode. This is repeated so that light of a predetermined wavelength is output from the second reflection film. In the optical resonant cavity, the temperature and the electric field are used for adjusting the refractive index of the electro-optic crystal together, so that the refractive index of the electro-optic crystal is changed rapidly along with the change of the electric field and the temperature, the preset refractive index is reached rapidly, and the wavelength tuning speed of the optical resonant cavity is improved; in addition, the change range of the refractive index of the temperature control electro-optic crystal is larger, so that the wavelength tuning range of the optical resonant cavity is also enlarged; furthermore, the combined action of temperature and electric field provides a smaller voltage applied to the first electrode and/or the second electrode by the optical resonator than adjusting the refractive index of the electro-optic crystal to a predetermined refractive index by the electric field alone, resulting in improved filtering.

Optionally, the temperature control structure is disposed on a side of the first reflective film away from the electro-optic crystal; and/or the temperature control structure is arranged on one side of the second reflecting film far away from the electro-optical crystal. In this alternative mode, the temperature control structure is arranged at the light-passing position, and the temperature applied to the electro-optic crystal by the temperature control structure is uniformly distributed on the plane perpendicular to the propagation direction, so that the temperature is better transmitted to the light-passing position of the electro-optic crystal, and the refractive index of the electro-optic crystal is better adjusted. Among these, the alternatives include the following three cases: in the first case, the temperature control structure generates resistance heat under the action of the current loop, the resistance heat is transmitted to the electro-optical crystal through the first reflecting film and the first electrode, so that the temperature control structure applies temperature to the electro-optical crystal, and the refractive index of the electro-optical crystal is changed under the action of the temperature. In the second case, the temperature control structure generates resistance heat under the action of the current loop, and the resistance heat is transmitted to the electro-optical crystal through the second reflecting film and the second electrode, so that the temperature control structure applies temperature to the electro-optical crystal, and the refractive index of the electro-optical crystal is changed under the action of the temperature. In the third case, the temperature control structure generates resistance heat under the action of the current loop, the resistance heat is transmitted to the electro-optical crystal through the first reflecting film and the first electrode and is also transmitted to the electro-optical crystal through the second reflecting film and the second electrode, so that the temperature control structure applies uniform temperature to the electro-optical crystal, and the refractive index of the electro-optical crystal is changed under the action of the temperature.

Optionally, the electro-optic crystal includes a light transmissive region and a non-light transmissive region; the first electrode and the second electrode are respectively arranged at two sides of the light transmission area of the electro-optic crystal along the propagation direction of the electro-optic crystal; the temperature control structure is arranged on one side or two sides of the non-light-transmitting area. In this alternative, the temperature control structure is arranged at the non-light-passing position, so that the requirement of the temperature control structure on the light transmittance is reduced, and the temperature control structure generates resistance heat under the action of the current loop, the resistance heat is directly transmitted to the electro-optical crystal, so that the temperature control structure applies temperature to the electro-optical crystal, and the refractive index of the electro-optical crystal is changed under the action of the temperature.

Optionally, the temperature control structure is disposed on one side of the electro-optic crystal along a direction parallel to the propagation direction, and/or the temperature control structure is disposed on the other side of the electro-optic crystal along a direction parallel to the propagation direction. In this alternative, the temperature control structure is arranged in a non-light passing position, so that the requirement of the temperature control structure on the light transmittance is reduced.

Optionally, the temperature control structure comprises a light transmissive resistive film.

Optionally, the material of the resistive film includes: indium tin oxide, ITO.

Optionally, the material of the electro-optic crystal comprises: lithium niobate, potassium niobate tantalate, lanthanum-doped lead zirconate titanate, lead magnesium niobate-lead titanate.

Optionally, in the propagation direction, the distance between the first reflective film and the second reflective film is equal to or greater than 50 micrometers and equal to or less than 300 micrometers. In this alternative, the size of the cavity length is inversely proportional to the free spectral range of the optical resonator, so to achieve a larger free spectral range, the cavity length can be reduced as much as possible, so the current cavity length needs to be 300 microns or less; then the electro-optic crystal may become brittle when the cavity length is too small, so the cavity length needs to be 50 microns or more.

Optionally, the material of the first electrode includes: indium tin oxide, ITO; the material of the second electrode includes: indium tin oxide, ITO.

In a second aspect, there is provided an optical filter comprising: a first optical fiber collimator, a second optical fiber collimator, and a plurality of optical resonators as described in any one of the first aspects above disposed on an optical path between the first optical fiber collimator and the second optical fiber collimator; the first optical fiber collimator is used for carrying out collimation treatment on received light rays to generate collimated light rays, and the collimated light rays sequentially pass through the plurality of optical resonant cavities along a first direction; the optical resonant cavities are used for carrying out filtering treatment on the collimated light rays and generating output filtered light rays containing preset wavelengths; any two optical resonant cavities in the plurality of optical resonant cavities have different cavity lengths; and a second fiber collimator for coupling the output filtered light to the fiber output. In the optical filter, since the cavity lengths of any two optical resonant cavities among the plurality of optical resonant cavities are different, and the refractive indexes of the electro-optical crystals in the plurality of optical resonant cavities are affected by both temperature and electric field, the wavelengths of light filtered out by any two optical resonant cavities among the plurality of optical resonant cavities are not identical, and the wavelengths of blocked light are different. For example, when two optical resonators are included in the plurality of optical resonators, it is assumed that the first optical resonator can filter out light having a wavelength λa and a wavelength λd, and block light having a wavelength other than λa and a wavelength λd; it is assumed that the second optical resonator filters out light having a wavelength λb and a wavelength λd, and blocks light having a wavelength other than λb and λd, so that the first optical resonator and the second optical resonator cooperate to filter out light having a wavelength λd, which is a predetermined wavelength, and the first optical resonator and the second optical resonator block light having a wavelength other than the predetermined wavelength. That is, when the plurality of optical resonators perform filtering processing on the straight light, more light rays with other wavelengths except the predetermined wavelength are blocked, and the generated output filtered light rays with the predetermined wavelength contain less light rays with other wavelengths except the predetermined wavelength, so that the filtering effect is improved.

Optionally, the optical path between the first optical fiber collimator and the second optical fiber collimator further includes: a first reflective element; the optical resonant cavities are specifically used for carrying out filtering treatment on the collimated light rays to generate first filtered light rays containing preset wavelengths; the first reflecting element is used for reflecting the first filtering light rays to the plurality of optical resonant cavities so that the first filtering light rays sequentially pass through the plurality of optical resonant cavities along a second direction, and the second direction is opposite to the first direction; the plurality of optical resonant cavities are also used for carrying out filtering treatment on the first filtering light rays reflected by the first reflecting element to generate output filtering light rays containing preset wavelengths. In this alternative manner, when the first filtered light is transmitted to the first reflecting element, the first reflecting element reflects the first filtered light to the plurality of optical resonant cavities, so that the first filtered light sequentially passes through the plurality of optical resonant cavities along the second direction, and the plurality of optical resonant cavities performs filtering processing on the first filtered light to generate output filtered light including a predetermined wavelength. Although the first filtered light contains less light with other wavelengths than the preset wavelength, the light with other wavelengths than the preset wavelength needs to be blocked, so that the plurality of optical resonant cavities further block the residual light with other wavelengths needing to be blocked in the first filtered light to generate output filtered light containing the preset wavelength, and the filtering effect is improved.

Optionally, the optical path between the first optical fiber collimator and the second optical fiber collimator further comprises a second reflecting element; the plurality of optical resonant cavities are specifically used for carrying out filtering treatment on the first filtering light rays reflected by the first reflecting element to generate second filtering light rays with preset wavelengths; the second reflecting element is used for reflecting the second filtering light rays to the plurality of optical resonant cavities so that the second filtering light rays sequentially pass through the plurality of optical resonant cavities along the first direction; the optical resonant cavities are also used for carrying out filtering treatment on the second filtering light rays reflected by the second reflecting element to generate output filtering light rays containing the preset wavelength. In this alternative, the second reflection element reflects the second filtered light to the plurality of optical resonant cavities, so that the plurality of optical resonant cavities filter the second filtered light, and therefore the plurality of optical resonant cavities further block the remaining light with other wavelengths to be blocked in the second filtered light, and generate output filtered light with predetermined wavelengths, so as to improve the filtering effect.

Optionally, the first reflecting element includes a first reflecting mirror and a second reflecting mirror, the first reflecting mirror is configured to receive the first filtered light, reflect the first filtered light to the second reflecting mirror, and the second reflecting mirror is configured to reflect the first filtered light reflected by the first reflecting mirror to the plurality of optical resonant cavities, where an included angle between the first reflecting mirror and the second reflecting mirror is greater than or equal to 89.5 degrees and less than or equal to 90.5 degrees.

Optionally, the first reflecting element comprises a right angle prism, and the right angle prism comprises a first right angle surface and a second right angle surface; the first right-angle surface is used for receiving the first filtered light, reflecting the first filtered light to the second right-angle surface, and reflecting the first filtered light reflected by the first right-angle surface to the plurality of optical resonant cavities, wherein the included angle between the first right-angle surface and the second right-angle surface is more than or equal to 89.5 degrees and less than or equal to 90.5 degrees.

Optionally, the second reflecting element includes a third reflecting mirror and a fourth reflecting mirror, and the third reflecting mirror is configured to receive the second filtered light and reflect the second filtered light to the fourth reflecting mirror; and the fourth reflector is used for reflecting the second filtered light rays reflected by the third reflector to the plurality of optical resonant cavities, wherein an included angle between the third reflector and the fourth reflector is more than or equal to 89.5 degrees and less than or equal to 90.5 degrees.

Optionally, the second reflecting element comprises a right angle prism, and the right angle prism comprises a third right angle surface and a fourth right angle surface; the third right-angle surface is used for receiving the second filtered light and reflecting the second filtered light to the fourth right-angle surface; and the fourth right angle surface is used for reflecting the second filtered light reflected by the third right angle surface to the plurality of optical resonant cavities, wherein the included angle between the third right angle surface and the fourth right angle surface is more than or equal to 89.5 degrees and less than or equal to 90.5 degrees.

Optionally, the difference in cavity length between any two of the plurality of optical resonators is greater than or equal to 5 microns. In this alternative, when the difference in the cavity lengths of any two of the plurality of optical resonators is 5 μm or more, the free spectral range of any two of the plurality of optical resonators will change so that the wavelengths of the filtered light of any two of the plurality of optical resonators are not exactly the same.

Drawings

FIG. 1 is a schematic diagram of an FP chamber provided by a first embodiment of the application;

fig. 2 is a schematic structural diagram of an optical network according to a first embodiment of the present application;

FIG. 3 is a schematic diagram of an optical performance monitor according to an embodiment of the present application;

FIG. 4 is a schematic diagram of an optical filter according to an embodiment of the present application;

fig. 5 is a schematic diagram of a first structure of an optical filter according to a second embodiment of the present application;

FIG. 6 is a schematic diagram illustrating a tuning mode of an optical resonator according to a second embodiment of the present application;

FIG. 7 is a schematic diagram of a second structure of an optical resonator according to a second embodiment of the present application;

FIG. 8 is a schematic diagram of a third structure of an optical resonator according to a second embodiment of the present application;

FIG. 9 is a schematic diagram of a fourth structure of an optical resonator according to a second embodiment of the present application;

FIG. 10 is a schematic diagram of a fifth embodiment of an optical resonator according to the second embodiment of the application;

FIG. 11 is a schematic diagram of a sixth structure of an optical resonator according to a second embodiment of the present application;

FIG. 12 is a schematic diagram of a seventh structure of an optical resonator according to a second embodiment of the present application;

FIG. 13 is a schematic diagram of an eighth structure of an optical resonator according to a second embodiment of the application;

FIG. 14 is a schematic diagram of a ninth structure of an optical resonator according to a second embodiment of the present application;

FIG. 15 is a schematic view of a tenth structure of an optical resonator according to a second embodiment of the present application;

FIG. 16 is a schematic view of an eleventh embodiment of an optical resonator according to the second embodiment of the application;

FIG. 17 is a schematic diagram of a twelfth structure of an optical resonator according to the second embodiment of the application;

fig. 18 is a schematic diagram of a first structure of an optical filter according to a third embodiment of the present application;

fig. 19 is a schematic view of a second structure of an optical filter according to a third embodiment of the present application;

fig. 20 is a schematic diagram of a third structure of an optical filter according to a third embodiment of the present application;

FIG. 21 is a simulation diagram of an optical filter according to a third embodiment of the present application;

fig. 22 is a schematic diagram of a first structure of an optical filter according to a fourth embodiment of the present application;

fig. 23 is a schematic diagram of a second structure of an optical filter according to a fourth embodiment of the present application;

FIG. 24 is a first simulation of an optical filter according to a fourth embodiment of the present application;

FIG. 25 is a second simulation of an optical filter according to a fourth embodiment of the present application;

FIG. 26 is a third simulation of an optical filter according to a fourth embodiment of the present application;

fig. 27 is a schematic diagram of a third structure of an optical filter according to a fourth embodiment of the present application.

Detailed Description

The technical solutions of the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In the present application, "plurality" means two or more. "and/or", describes an association relationship of an association object, and indicates that there may be three relationships, for example, a and/or B, and may indicate: a alone, a and B together, and B alone, wherein a, B may be singular or plural. The character "/" generally indicates that the context-dependent object is an "or" relationship. In addition, in the embodiments of the present application, the words "first", "second", and the like do not limit the number and order.

In the present application, the words "exemplary" or "such as" are used to mean serving as an example, instance, or illustration. Any embodiment or design described herein as "exemplary" or "for example" should not be construed as preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "such as" is intended to present related concepts in a concrete fashion.

Technical terms provided in the embodiments of the present application are described as follows:

electro-optic effect: under the action of the external electric field, the refractive index of the electro-optic crystal is changed. The linear electro-optic effect is that the variation of the refractive index of the electro-optic crystal is in linear relation with the electric field, and the secondary electro-optic effect is that the variation of the refractive index of the electro-optic crystal is in linear relation with the square of the electric field. The linear electro-optic effect of the electro-optic crystal is divided into two kinds of longitudinal electro-optic effect and transverse electro-optic effect. The longitudinal electro-optic effect is an electro-optic effect generated when the direction of an electric field applied to the electro-optic crystal is parallel to the propagation direction of light in the electro-optic crystal; the transverse electro-optic effect is an electro-optic effect that occurs when the direction of an electric field applied to the electro-optic crystal is perpendicular to the direction of propagation of light in the electro-optic crystal.

Fabry-perot cavity: in short, referring to fig. 1, an embodiment of the present application provides a schematic diagram of an FP cavity 10, in the FP cavity 10, two reflecting surfaces, that is, a reflecting surface 101 and a reflecting surface 102 are provided, respectively, the reflecting surface 101 is disposed opposite to the reflecting surface 102, and an optical medium 103 (for example, glass, air, electro-optical crystal, etc.) is filled between the reflecting surface 101 and the reflecting surface 102. When an incident light ray having a wavelength λ1 is incident on the reflection surface 101 at an incident angle α, a part of the incident light ray having a wavelength λ1 is reflected to form a reflected light ray, the reflected light ray cannot enter the optical medium 103, and another part of the incident light ray having a wavelength λ1 is transmitted to the optical medium 103 to form a transmitted light ray. The optical medium 103 transmits the transmitted light to the reflection surface 102 with the refractive index n of the optical medium 103, the reflection surface 102 transmits light having the wavelength of a predetermined wavelength λ out of the transmitted light out of the reflection surface 102, and the reflection surface 102 reflects light having other wavelengths than the light having the wavelength of the predetermined wavelength λ out of the transmitted light to the optical medium 103, and the optical medium 103 transmits light having other wavelengths to the reflection surface 101, so that the FP cavity 10 filters out light having the wavelength of the predetermined wavelength λ out of the incident light having the wavelength of λ1, thereby realizing a filtering effect. Specifically, the interference effect occurs during the back and forth reflection between the reflecting surface 101 and the reflecting surface 102, so that the light transmitted out of the reflecting surface 102 actually belongs to the light generated by the interference of the transmitted light. Where the FP cavity 10 has a cavity length L, assuming a thickness L of the optical medium 103. Then, the predetermined wavelength λ satisfies the following equation 1.

2nlcosα=mλ (m=1, 2,3 …) (formula 1).

In formula 1, m is specifically an interference order, and is an integer.

Referring to equation 1, it can be seen that when the wavelength of the light to be filtered out by the FP cavity 10 is changed, the cavity length L of the FP cavity 10, the refractive index n of the optical medium 103, or the incident angle α of the incident light can be adjusted.

Wherein in the FP cavity 10 the spectrum of light of the predetermined wavelength filtered out by the FP cavity 10 is periodic and the difference between the wavelength of the nth filtered out light and the wavelength of the n+1th filtered out light represents the free spectral range (free spectral range, FSR) of the FP cavity 10. The FSR of FP cavity 10 is expressed as Deltav, then Deltav satisfies equation 2 below.

Δv=c/(2 nL) (formula 2).

In formula 2, c represents the speed of light.

Referring to equation 2, the free spectral range FSR of the FP cavity 10 is related to the cavity length L of the FP cavity 10 and the refractive index n of the optical medium 103 in the FP cavity 10.

In addition, the difference between the peaks and the valleys of the light of the predetermined wavelength filtered out by the FP cavity 10 is related to the reflectivities of the reflective surface 101 and the reflective surface 102.

The optical fiber transmission uses light as a carrier wave, and uses an optical fiber as a transmission medium to transmit signals. Among them, a backbone network is a high-speed network for connecting a plurality of areas or regions, and in the backbone network, optical fiber transmission is generally used. With the development of communication technology and the increase of data transmission requirements, reconfigurable optical add-drop multiplexers (ROADMs) in backbone networks need to sink to metropolitan area networks to achieve the purpose of network upgrade. In general, the reconfigurable optical add/drop multiplexer needs to use an optical performance monitor (optical performance monitor, OPM) to detect the signal-to-noise ratio and power of the optical signal transmitted by the optical fiber, so as to ensure that the crosstalk level and the bit error rate of the optical signal transmitted by the optical fiber are controllable.

Referring to fig. 2, an embodiment of the present application provides a schematic structural diagram of an optical network 20, where the optical network 20 includes a network 1 and a network 2, where a plurality of optical amplifiers and a plurality of optical cross connect devices are connected to the network 1 through optical fibers, the optical amplifiers are used to amplify optical signals transmitted in the optical fibers, the optical cross connect devices are used to provide optical communication services for a predetermined area (for example, an area covered by a small building or a large building as shown in fig. 2) and/or a network (for example, the network 2 shown in fig. 2), and in the network 1, a plurality of optical performance monitors OPM are further included, for example, the optical performance monitor OPM1, the optical performance monitor OPM2, and the optical performance monitor OPM3 shown in fig. 2, where each optical performance monitor is used to detect a signal-to-noise ratio and power of the optical signals transmitted by a certain number of optical amplifiers and/or the optical cross connect devices. The network 2 communicates with the optical cross-connect device in the network 1 through the optical cross-connect device in the network 2, so that the network 2 obtains an optical signal transmitted in the network 1, or transmits an optical signal generated by a certain transceiver in the network 2 to the network 1. A plurality of optical amplifiers and a plurality of optical cross-connect devices are also connected to the network 2, and a plurality of optical performance monitors OPM, such as the optical performance monitor OPM4 and the optical performance monitor OPM5 shown in fig. 2, are also included in the network 2, each for detecting the signal-to-noise ratio and the power of the optical signals transmitted by a certain number of optical amplifiers and/or optical cross-connect devices. In addition, in the network 2, the optical add/drop multiplexer ROADM may be further included, where the reconfigurable optical add/drop multiplexer ROADM is connected to the combiner 201 through the optical fiber 202, the combiner 201 receives a plurality of optical signals with wavelengths sent by different transceiver devices, combines the plurality of optical signals with wavelengths into a beam of optical signals with a unified wavelength, and transmits the beam of optical signals to the reconfigurable optical add/drop multiplexer ROADM through the optical fiber 202, where the wavelength of the beam of optical signals is adjusted by the reconfigurable optical add/drop multiplexer ROADM, so that the beam of optical signals can be transmitted in the network 2 and does not cross-talk with other optical signals transmitted in the network 2. The reconfigurable optical add/drop multiplexer ROADM is also connected to the demultiplexer 203 through the optical fiber 204, and the reconfigurable optical add/drop multiplexer ROADM obtains an optical signal to be sent to the demultiplexer 203 from the network 2, and transmits the optical signal to the demultiplexer 203 through the optical fiber 204, so that the demultiplexer 203 demultiplexes the optical signal and sends the optical signal to different transceiver devices. The optical signal generated by the multiplexer 201, the optical signal received by the demultiplexer 203, and the optical signal transmitted by the optical fiber 204 are also detected by the optical performance monitor OPM6 in terms of signal-to-noise ratio and power.

Referring to fig. 3, an embodiment of the present application provides a schematic structural diagram of an optical performance monitor 30, in the optical performance monitor 30, a core component of the optical performance monitor 30 is an optical filter (tunableoptical filter, TOF), referring to fig. 3, the optical performance monitor 30 includes an optical filter 301, a detector 302 and a data processing structure 303, where the optical filter 310 performs filtering processing on an input optical signal to obtain an optical signal with a predetermined wavelength; the detector 302 photoelectrically converts the filtered optical signal to generate an electrical signal; the data processing structure 303 processes the electric signal generated by the detector 302, calculates various parameter indexes of the electric signal, and outputs the monitoring result.

The optical signal is generated by modulating a transmission signal on an optical wave. Furthermore, the optical filter TOF may filter not only the optical signal, but also a plurality of light waves of different wavelengths, and for clarity, embodiments of the present application collectively refer to the optical signal and/or the light waves as light rays.

Referring to fig. 4, an embodiment of the present application provides an optical filter 40, in which an optical filter 40 includes an optical fiber collimator 401, an FP cavity 402, an FP cavity 403, and an optical fiber collimator 404, wherein the FP cavity 402 includes an electro-optical crystal 4021, indium Tin Oxide (ITO) electrodes 4022 and 4023 respectively provided on both sides of the electro-optical crystal 4021 in a propagation direction of the electro-optical crystal 4021, a reflective film 4024 provided on a side of the ITO electrode 4022 away from the electro-optical crystal 4021, and a reflective film 4025 provided on a side of the ITO electrode 4023 away from the electro-optical crystal 4021; the FP cavity 403 includes an electro-optic crystal 4031, indium Tin Oxide (ITO) electrodes 4032 and ITO electrodes 4033 disposed on both sides of the electro-optic crystal 4031 in a propagation direction of the electro-optic crystal 4031, a reflective film 4034 disposed on a side of the ITO electrodes 4032 away from the electro-optic crystal 4031, and a reflective film 4035 disposed on a side of the ITO electrodes 4033 away from the electro-optic crystal 4031. Wherein FP cavity 402 is of a different cavity length than FP cavity 403.

The optical filter 40 operates on the principle that: the fiber collimator 401 transmits the input light to the FP cavity 402 and FP cavity 403; the electro-optic crystal 4021 in FP cavity 402 has a first refractive index such that FP cavity 402 first filters the input light at the first refractive index; the electro-optic crystal 4031 in the FP cavity 403 has a second refractive index such that the FP cavity 403 second filters the input light at the second refractive index to generate a filtered light, which is output through the fiber collimator 404.

Wherein, in order to change the wavelength of the filtered light outputted from the fiber collimator 404, the magnitude of the voltage applied between the ITO electrode 4022 and the ITO electrode 4023 in the FP cavity 402 may be adjusted to adjust the first refractive index of the electro-optic crystal 4021 in the FP cavity 402; and/or adjusting the magnitude of the voltage applied between the ITO electrode 4032 and the ITO electrode 4033 in the FP cavity 403 to adjust the second refractive index of the electro-optic crystal 4031 in the FP cavity 403. However, the manner in which the magnitude of the applied voltage and thus the refractive index of the FP cavity is adjusted results in a limited wavelength tuning range for the light filtered out by the FP cavity and requires a higher applied voltage.

To address the problem of limited wavelength tuning range of FP cavities, embodiments of the present application provide an optical resonator, as shown with reference to fig. 5, fig. 5 shows a front view of an optical resonator 50, where the optical resonator 50 includes: an electro-optic crystal 501; an electrode 502 and an electrode 503, wherein the electrode 502 and the electrode 503 are disposed on both sides of the electro-optic crystal 501 along the propagation direction of the electro-optic crystal 501, respectively; the electrodes 502 and 503 apply an electric field to the electro-optic crystal 501, which is used to adjust the refractive index of the electro-optic crystal 501, the electric field having a component parallel to the propagation direction. A reflection film 504 and a reflection film 505, wherein the reflection film 504 is provided on a side of the electrode 502 away from the electro-optical crystal 501, and the reflection film 505 is provided on a side of the electrode 503 away from the electro-optical crystal 501; a temperature control structure 506, wherein the temperature control structure 506 applies a temperature to the electro-optic crystal 501 to adjust the refractive index of the electro-optic crystal 501.

Specifically, referring to the optical resonator 50 shown in fig. 5, in the optical resonator 50, the propagation direction of the electro-optical crystal 501 is the direction in which-x is directed x, and the propagation directions of the electrode 502 and the electrode 503 in the direction in which-x is directed x are respectively provided on both sides of the electro-optical crystal 501. The material of the electrode 502 and the electrode 503 is a transparent conductive material, and more specifically, the material of the electrode 502 and the electrode 503 may be indium tin oxide. And, the coverage area of the electrode 502 in the propagation direction is larger than the coverage area of the reflective film 504 in the propagation direction, and the coverage area of the electrode 503 in the propagation direction is larger than the coverage area of the reflective film 505 in the propagation direction. Then, a wire 502a is provided in the electrode 502 and a wire 503a is provided in the electrode 503 by a wire bonding (also referred to as pressure bonding, binding, bonding, wire bonding) process; or the lead 502a is provided in the electrode 502 by bonding with glue, and the lead 503a is provided in the electrode 503. When electrode 502 is then connected to the positive voltage terminal via wire 502a and electrode 503 is connected to the negative voltage terminal via wire 503a, an electric field E is formed between electrode 502 and electrode 503, the direction of the electric field E being directed in the x direction along-x, i.e. the direction of the electric field E is parallel to the propagation direction. The material of the electro-optic crystal 501 includes any one of the following: lithium niobate, potassium niobate, lanthanum-doped lead zirconate titanate, lead magnesium niobate-lead titanate, which have an electro-optic effect, so that the electro-optic crystal 501 generates an electro-optic effect under the action of the electric field E, more specifically, the electro-optic crystal 501 generates a longitudinal electro-optic effect under the action of the electric field E, and then the refractive index of the electro-optic crystal 501 is changed under the action of the electric field E.

In addition, the optical resonator 50 further includes a temperature control structure 506, referring to the schematic structural diagram of the optical resonator 50 shown in fig. 5, wherein the temperature control structure 506 is disposed on a side of the reflective film 504 away from the electro-optical crystal 501. Wire bonding (also known as pressure bonding, wire bonding) processes provide wires 506a at a first end of temperature controlled structure 506, wires 506b at a second end of temperature controlled structure 506, or wires 506a at a first end of temperature controlled structure 506 and wires 506b at a second end of temperature controlled structure 506. Then the first end of the temperature control structure 506 is connected to the positive power supply through a wire 506a, and the second end of the temperature control structure 506 is connected to the negative power supply through a wire 506b, so that a current loop is formed in the temperature control structure 506, and the temperature control structure 506 includes a light-transmitting resistive film, specifically, the materials of the resistive film include: indium tin oxide. Then, the resistive film in the temperature control structure 506 will generate resistive heat under the action of the current loop, which is transferred to the electro-optic crystal 501 through the reflective film 504 and the electrode 502, so that the temperature control structure applies a temperature to the electro-optic crystal 501, and the refractive index of the electro-optic crystal 501 will change under the action of the temperature.

Referring to fig. 6, embodiments of the present application provide the effect of an electro-optic crystal 501 in different modes of adjustment. In the first case, when an electric field E is formed only between the electrode 502 and the electrode 503, the refractive index of the electro-optic crystal 501 is changed rapidly with the change of the electric field E, and the adjustment speed is fast; however, in order to bring the electric field E to a predetermined requirement, a large voltage needs to be applied to the electrode 502 and/or the electrode 502, and in this case, the electric field E controls the variation range of the refractive index of the electro-optic crystal 501 to be limited, so that the wavelength tuning range of the optical resonator 50 is limited. In the second case, when only two ends of the temperature control structure 506 are connected to the power supply, so that the temperature control structure 506 generates resistance heat, and temperature is applied to the electro-optic crystal 501, the refractive index of the electro-optic crystal 501 changes along with the change of temperature, and the power supply connected with the temperature control structure 506 does not need to provide larger voltage to the temperature control structure 506, different resistance heat can be generated under the driving of smaller voltage, so as to transmit different temperatures to the electro-optic crystal 501, and the change range of the refractive index of the temperature control electro-optic crystal 501 is larger, so that the wavelength tuning range of the optical resonant cavity 50 is larger; however, by connecting the temperature control structure 506 to a power source, the temperature control structure 506 provides the electro-optic crystal 501 with the temperature required to adjust the refractive index, which may take some time to make the temperature adjustment of the refractive index of the electro-optic crystal 501 slower. In a third case, an electric field E is formed between the electrode 502 and the electrode 503, and both ends of the temperature control structure 506 are also connected to a power supply, so that the temperature control structure 506 generates resistance heat, and temperature is applied to the electro-optical crystal 501; in this case, the temperature and the electric field are used together to adjust the refractive index of the electro-optic crystal 501, so that the refractive index of the electro-optic crystal 501 is changed rapidly along with the change of the electric field E and the temperature, and the required refractive index is reached rapidly, thereby improving the wavelength tuning speed of the optical resonant cavity; in addition, the change range of the refractive index of the temperature control electro-optic crystal is larger, so that the wavelength tuning range of the optical resonant cavity is also enlarged; furthermore, the combined action of temperature and electric field may apply a smaller voltage to electrode 502 and/or electrode 503 than would be applied by the electric field alone to adjust the refractive index of electro-optic crystal 501 to the desired refractive index.

Illustratively, in order to make the filtering effect of the optical resonator 50 better, the distance L1 between the reflective film 504 and the reflective film 505, that is, the cavity length of the optical resonator 50, is required to be 50 micrometers (um) or more and 300 micrometers (um) or less. Referring to equation 2, the size of the cavity length is inversely proportional to the free spectral range of the optical resonator, so in order to achieve a larger free spectral range, the cavity length can be reduced as much as possible, and thus the current cavity length is recommended to be 300 μm or less; then the electro-optic crystal 501 may become brittle when the cavity length is too small, thus suggesting a cavity length of 50 microns or more.

The optical resonant cavity 50 operates on the following principle:

when an input light ray is incident on the reflective film 504 in the propagation direction (i.e., the incident direction), the reflective film 504 serves to transmit the input light ray in the propagation direction, and the transmitted light ray is transmitted to the electro-optical crystal 501 through the electrode 502. Illustratively, the reflective film 504 reflects a portion of the input light to form reflected light that is not transmitted through the electrode 502 to the electro-optic crystal 501; the reflective film 504 transmits another portion of the input light to form a transmitted light, which is transmitted through the electrode 502 to the electro-optic crystal 501.

An electro-optical crystal 501 for transmitting light transmitted by the reflective film 504 to the reflective film 505 through the electrode 503 at a predetermined refractive index under the action of temperature and an electric field E. As described above, when a current loop is formed in the temperature control structure 506, the temperature control structure 506 applies a temperature to the electro-optic crystal 501, the refractive index of the electro-optic crystal 501 changes due to the temperature, and when the electrode 502 and the electrode 503 are connected to different voltage terminals to form an electric field E, the refractive index of the electro-optic crystal 501 also changes due to the electric field E. Assuming that the refractive index of the electro-optic crystal 501 becomes a predetermined refractive index n1 under the combined action of the electric field E and the temperature, the predetermined refractive index n1 changes when the magnitude of the electric field E and the temperature change, and the input light rays incident along a fixed incident angle will be transmitted at different refractive angles for different distances in the electro-optic crystal 501.

A reflection film 505 for outputting light of a predetermined wavelength among light transmitted from the electro-optical crystal 501 and reflecting light of other wavelengths than the predetermined wavelength to the electro-optical crystal 501 through the electrode 503; the light rays with the predetermined wavelength that can be transmitted satisfy the above formula 1, in the optical resonator 50, the refractive index n substituted in the formula 1 is the predetermined refractive index n1 formed under the combined action of the electric field E and the resistive heat, the cavity length L substituted in the formula 1 is the distance L1 between the reflective film 504 and the reflective film 505, the incident angle α substituted in the formula 1 is the incident angle α1 of the incident light rays, and in the optical resonator 50, the incident angle α1 of the incident light rays is 0, so that a specific value of the predetermined wavelength can be calculated, and the reflective film 505 outputs the light rays with the predetermined wavelength. Light of a wavelength other than the predetermined wavelength is transmitted to the electro-optical crystal 501 through the electrode 503 at the predetermined refractive index n 1.

The electro-optical crystal 501 is further configured to transmit the light reflected by the reflective film 505 to the reflective film 504 through the electrode 502 at a predetermined refractive index n 1; the reflective film 504 is also used to reflect light transmitted by the electro-optic crystal 501 to the electro-optic crystal 501 through the electrode 502.

For example, in the optical resonator 50, assuming that the reflectance of the material of the reflective film 504 and the reflective film 505 is required to be m, the reflective film 504 and the reflective film 505 may be directly made of the material having the reflectance of m. Alternatively, when the reflectance of the material of the electrode 502 and the electrode 503 is x, then the reflective film 504 and the reflective film 505 may be made of a material having a reflectance of m—x.

In the optical resonator described above, by providing the first electrode (i.e., electrode 502) and the second electrode (i.e., electrode 503) on both sides of the electro-optic crystal along the propagation direction of the electro-optic crystal, respectively, an electric field is formed in the electro-optic crystal when a driving voltage is applied to the first electrode and the second electrode, and the electric field has a component parallel to the propagation direction, and the refractive index of the electro-optic crystal is changed by the electric field. And a first reflective film (i.e., reflective film 504) is provided on the side of the first electrode remote from the electro-optic crystal and a second reflective film (i.e., reflective film 505) is provided on the side of the second electrode remote from the electro-optic crystal such that the first reflective film, the second reflective film, and the electro-optic crystal filter the input light. And a temperature control structure is also arranged on the electro-optic crystal, the temperature control structure is connected to a power supply to form a current loop, and resistance heat is generated under the action of the current loop, and the resistance heat forms the temperature transmitted to the electro-optic crystal. The refractive index of the electro-optic crystal will become a predetermined refractive index under the combined action of temperature and electric field. Then, when the electric field intensity and the temperature in the electro-optic crystal are different, the input light transmitted by the first reflective film in the propagation direction is transmitted to the electro-optic crystal through the first electrode, and the electro-optic crystal is transmitted to the second reflective film through the second electrode at a predetermined refractive index corresponding to the electric field intensity and the temperature in the electro-optic crystal. The second reflecting film outputs light rays with a preset wavelength in the light rays transmitted through the electro-optical crystal, namely, the light rays with the preset wavelength are transmitted out of the second reflecting film, and the light rays with other wavelengths except the preset wavelength are reflected back to the electro-optical crystal through the second electrode, so that the electro-optical crystal transmits the light rays reflected by the second reflecting film to the first reflecting film through the first electrode with a preset refractive index, and the first reflecting film is further used for reflecting the light rays transmitted by the electro-optical crystal to the electro-optical crystal through the first electrode. This is repeated so that light of a predetermined wavelength is output from the second reflection film. In the optical resonant cavity, the temperature and the electric field are used for adjusting the refractive index of the electro-optic crystal together, so that the refractive index of the electro-optic crystal is changed rapidly along with the change of the electric field and the temperature, the preset refractive index is reached rapidly, and the wavelength tuning speed of the optical resonant cavity is improved; in addition, the change range of the refractive index of the temperature control electro-optic crystal is larger, so that the wavelength tuning range of the optical resonant cavity is also enlarged; furthermore, the combined action of temperature and electric field provides a smaller voltage applied to the first electrode and/or the second electrode by the optical resonator than adjusting the refractive index of the electro-optic crystal to a predetermined refractive index by the electric field alone, resulting in improved filtering.

Referring to fig. 7, an embodiment of the present application provides a second schematic structural view of the optical resonant cavity 50, where the temperature control structure 506 may be disposed on a side of the reflective film 505 away from the electro-optical crystal 501, and when the temperature control structure 506 is connected to a power source to form a current loop, the temperature control structure 506 includes an optically transparent resistive film, and specifically, the resistive film includes: indium tin oxide. Then, the resistive film in the temperature control structure 506 will generate resistive heat under the action of the current loop, which is transmitted to the electro-optic crystal 501 through the reflective film 505 and the electrode 503, so that the temperature control structure 506 applies temperature to the electro-optic crystal 501, and the refractive index of the electro-optic crystal 501 will change under the action of the temperature.

Referring to fig. 8, an embodiment of the present application provides a third schematic structure of the optical resonant cavity 50, where the temperature control structure 506 includes two parts, and the first part 5061 of the temperature control structure 506 may be disposed on a side of the reflective film 504 away from the electro-optic crystal 501, and when the first part 5061 of the temperature control structure 506 is connected to the power source 1 to form a current loop, the first part of the temperature control structure 506 generates resistive heat under the effect of the current loop, and the resistive heat is transmitted to the electro-optic crystal 501 through the reflective film 504 and the electrode 502, so that the first part 5061 of the temperature control structure 506 applies a temperature to the electro-optic crystal 501, and the refractive index of the electro-optic crystal 501 changes under the effect of the temperature. The second portion 5062 of the temperature control structure 506 may be disposed on a side of the reflective film 505 remote from the electro-optic crystal 501, and when the second portion 5062 of the temperature control structure 506 is connected to the power source 2 to form a current loop, the second portion 5062 of the temperature control structure 506 generates resistive heat that is transmitted to the electro-optic crystal 501 through the reflective film 505 and the electrode 503, such that the second portion 5062 of the temperature control structure 506 applies a temperature to the electro-optic crystal 501, and the refractive index of the electro-optic crystal 501 changes under the effect of the temperature.

For example, referring to fig. 8, the first end of the first portion 5061 of the temperature control structure 506 and the first end of the second portion 5062 of the temperature control structure 506 may be connected by a wire, and then the second end of the first portion 5061 of the temperature control structure 506 and the second end of the second portion 5062 of the temperature control structure 506 may be connected to the power source 1 by a wire (or the power source 2, that is, the current first portion 5061 of the temperature control structure 506 and the current second portion 5062 of the temperature control structure 506 may be connected to the same power source), then the first portion 5061 of the temperature control structure 506 and the second portion 5062 of the temperature control structure 506 may be in the same current loop, and the temperature change magnitudes of the two portions may be the same, so that the first portion 5061 of the temperature control structure 506 and the second portion 5062 of the temperature control structure 506 may apply a more uniform temperature to the electro-optic crystal 501, and increase the speed of temperature change.

For example, although in the optical resonator 50 shown in fig. 5 to 8, the temperature control structure 506 is disposed not in direct contact with the electro-optical crystal 501, in another possible implementation, the light passing surface of the electro-optical crystal 501 in the propagation direction is defined as an incident surface, and the light emitting surface of the electro-optical crystal 501 in the propagation direction is defined as an emitting surface, the temperature control structure 506 may be disposed on any one of a non-incident surface and a non-emitting surface in the electro-optical crystal 501, and the temperature control structure 506 is in direct contact with the electro-optical crystal 501. The arrangement direction of the temperature control structures 506 and the number of the temperature control structures 506 are not limited in the embodiments of the present application.

Referring to FIG. 9, an embodiment of the present application provides a fourth structural schematic diagram of an optical resonator 50, in which optical resonator 50 an electro-optic crystal 501 includes a light-transmitting region 501a and a non-light-transmitting region 501b; wherein the electrode 502 and the electrode 503 are respectively disposed at two sides of the light-transmitting region 501a of the electro-optic crystal along the propagation direction of the electro-optic crystal; the temperature control structure 506 is disposed on one side of the non-transparent region 501 b. Specifically, the light passing surface of the electro-optical crystal 501 along the propagation direction is defined as an incident surface, the light emitting surface of the electro-optical crystal 501 along the propagation direction is defined as an emergent surface, the temperature control structure 506 is disposed in the non-light transmitting area 501b of the incident surface of the electro-optical crystal 501, when the temperature control structure 506 is connected to a power supply to form a current loop, the temperature control structure 506 generates resistance heat under the action of the current loop, and the resistance heat is directly transmitted to the electro-optical crystal 501, so that the temperature is applied to the electro-optical crystal 501 by the temperature control structure 506, and the refractive index of the electro-optical crystal 501 is changed under the action of the temperature.

Referring to FIG. 10, an embodiment of the present application provides a fifth structural schematic diagram of an optical resonator 50, in which an electro-optic crystal 501 includes a light-transmitting region 501a and a non-light-transmitting region 501b in the optical resonator 50; wherein the electrode 502 and the electrode 503 are respectively disposed at two sides of the light-transmitting region 501a of the electro-optic crystal along the propagation direction of the electro-optic crystal; the temperature control structure 506 is disposed on one side of the non-transparent region 501 b. Specifically, the light passing surface of the electro-optical crystal 501 along the propagation direction is defined as an incident surface, the light emitting surface of the electro-optical crystal 501 along the propagation direction is defined as an emergent surface, the temperature control structure 506 is disposed in the non-light transmitting area 501b of the emergent surface of the electro-optical crystal 501, and when the temperature control structure 506 is connected to a power supply to form a current loop, the temperature control structure 506 generates resistance heat under the action of the current loop, and the resistance heat is directly transmitted to the electro-optical crystal 501, so that the temperature is applied to the electro-optical crystal 501 by the temperature control structure 506, and the refractive index of the electro-optical crystal 501 is changed under the action of the temperature.

Referring to FIG. 11, an embodiment of the present application provides a fifth structural schematic diagram of an optical resonator 50, in which an electro-optic crystal 501 includes a light-transmitting region 501a and a non-light-transmitting region 501b in the optical resonator 50; wherein the electrode 502 and the electrode 503 are respectively disposed at two sides of the light-transmitting region 501a of the electro-optic crystal along the propagation direction of the electro-optic crystal; the temperature control structures 506 are disposed on two sides of the non-transparent region 501 b. Specifically, when the light passing surface of the electro-optical crystal 501 along the propagation direction is defined as an incident surface, the light exiting surface of the electro-optical crystal 501 along the propagation direction is defined as an exit surface, and the first portion 5061 of the temperature control structure 506 is disposed in the non-light transmitting area 501b of the incident surface of the electro-optical crystal 501, when the first portion 5061 of the temperature control structure 506 is connected to the power supply 1 to form a current loop, resistive heat is generated by the first portion of the temperature control structure 506 under the action of the current loop, and the resistive heat is directly transmitted to the electro-optical crystal 501, so that the first portion 5061 of the temperature control structure 506 applies a temperature to the electro-optical crystal 501, and the refractive index of the electro-optical crystal 501 is changed under the action of the temperature. When the second portion 5062 of the temperature control structure 506 is connected to the power supply 2 to form a current loop, the second portion 5062 of the temperature control structure 506 will generate resistive heat under the influence of the current loop, which is directly transferred to the electro-optic crystal 501, so that the second portion 5062 of the temperature control structure 506 applies a temperature to the electro-optic crystal 501, and the refractive index of the electro-optic crystal 501 will change under the influence of the temperature.

For example, referring to fig. 11, the first end of the first portion 5061 of the temperature control structure 506 and the first end of the second portion 5062 of the temperature control structure 506 may be connected by a wire, and then the second end of the first portion 5061 of the temperature control structure 506 and the second end of the second portion 5062 of the temperature control structure 506 may be connected to the power source 1 by a wire (or the power source 2, that is, the current first portion 5061 of the temperature control structure 506 and the current second portion 5062 of the temperature control structure 506 may be connected to the same power source), then the first portion 5061 of the temperature control structure 506 and the second portion 5062 of the temperature control structure 506 may be in the same current loop, and the temperature change amplitude of the two portions may be the same, so that the first portion 5061 of the temperature control structure 506 and the second portion 5062 of the temperature control structure 506 may apply a more uniform temperature to the electro-optic crystal 501, and increase the speed of temperature change.

The temperature control structure 506 may also be arranged on one side of the electro-optic crystal parallel to the propagation direction, as shown in fig. 12, in particular, the z-side of the electro-optic crystal 501 according to the arrangement position of the optical resonator shown in fig. 12, and the temperature control structure 506 may also be arranged on the other side of the electro-optic crystal parallel to the propagation direction, as shown in fig. 13, in particular, the-z-side of the electro-optic crystal 501 according to the arrangement position of the optical resonator shown in fig. 13. Alternatively, referring to fig. 14, the temperature control structure 506 includes two portions, and the first portion 5061 of the temperature control structure 506 may be disposed on one side of the electro-optic crystal 501 in parallel to the propagation direction, and the second portion 5062 of the temperature control structure 506 may be disposed on the other side of the electro-optic crystal 501 in parallel to the propagation direction. Specifically, a first portion 5061 of the temperature control structure 506 is disposed on the z-side of the electro-optic crystal 501 and a second portion 5062 of the temperature control structure 506 is disposed on the-z-side of the electro-optic crystal 501.

Referring to fig. 15, the temperature control structure 506 may also be disposed on a side of the electro-optic crystal parallel to the propagation direction, and in particular, the side may be the y side of the electro-optic crystal 501 according to the placement position of the optical resonator shown in fig. 15. Referring to fig. 16, the temperature control structure 506 may also be disposed on the other side of the electro-optic crystal parallel to the propagation direction, and in particular, the other side may be the-y side of the electro-optic crystal 501 according to the placement position of the optical resonator shown in fig. 16. Alternatively, referring to fig. 17, the temperature control structure 506 includes two portions, and the first portion 5061 of the temperature control structure 506 may be disposed on one side of the electro-optic crystal 501 in parallel to the propagation direction, and the second portion 5062 of the temperature control structure 506 may be disposed on the other side of the electro-optic crystal 501 in parallel to the propagation direction. Specifically, a first portion 5061 of the temperature control structure 506 is disposed on the y-side of the electro-optic crystal 501, and a second portion 5062 of the temperature control structure 506 is disposed on the-y-side of the electro-optic crystal 501.

Fig. 5 to 14 are front views of the optical resonator 50, and fig. 15 to 17 are top views of the optical resonator 50. The temperature control structure can be selected and arranged according to actual requirements, and the embodiment of the application does not limit the arrangement positions of the temperature control structure and the part contained in the temperature control structure.

In addition, an embodiment of the present application also provides an optical filter, as shown with reference to fig. 18, wherein the optical filter 11 includes an optical fiber collimator 60a on an input side, an optical fiber collimator 60b on an output side, and a plurality of optical resonators 50 disposed on an optical path between the optical fiber collimator 60a and the optical fiber collimator 60 b. Wherein each of the plurality of optical resonators 50 is the optical resonator 50 described above, more specifically, the optical resonator 50c includes the optical resonator 50a and the optical resonator 50b, the optical resonator 50a and the optical resonator 50b may be any of the optical resonators 50 described above, and in the placement position of the optical filter 11 shown in fig. 18, the optical fiber collimator 60a, the optical resonator 50b, and the optical fiber collimator 60b are sequentially disposed in a first direction from-x to-x, in fig. 18, the optical path is a solid line with an arrow, and in the optical path, the optical fiber collimator 60a is located on a first side of the plurality of optical resonators 50, and the optical fiber collimator 60b is located on a second side of the optical resonator 50 c. In order to make the free spectral ranges of any two of the plurality of optical resonators 50 different, the cavity lengths of any two of the plurality of optical resonators 50 need to be set different. More specifically, the difference in cavity length between the optical resonator 50a and the optical resonator 50b is 5um or more.

The optical fiber collimator 60a is provided with an optical fiber 601a, the optical fiber 601a is used for transmitting input light, the optical fiber collimator 60b is provided with an optical fiber 601b, and the optical fiber 601b is used for transmitting output light.

Then, the optical fiber collimator 60a is configured to collimate the received light (i.e. the input light transmitted by the optical fiber 601 a) to generate collimated light, and sequentially pass the collimated light through the plurality of optical resonators along the first direction. And the optical resonant cavities are used for carrying out filtering treatment on the collimated light rays and generating output filtered light rays containing a preset wavelength.

Illustratively, the light received by the fiber collimator 60a includes a plurality of light rays of different wavelengths, including light rays of wavelength λa, light rays of wavelength λb, light rays of wavelength λc and light rays of wavelength λd, and the fiber collimator 60a collimates the light rays of different wavelengths to generate collimated light rays, so that the collimated light rays still include light rays of wavelength λa, light rays of wavelength λb, light rays of wavelength λc and light rays of wavelength λd, wherein each of the light rays of different wavelengths passes through the optical resonant cavity 50a in the first direction at the same incident angle α2. The incident angle α2 may be, for example, 0 degrees. Illustratively, embodiments of the present application are not limited to the angle at which the collimated light is incident on the optical cavity 50 b.

Assuming that the light with the predetermined wavelength is the light with the wavelength λd, in an ideal state, that means that the plurality of optical resonators 50 need to filter out the light with the wavelength λd in the collimated light, when the driving voltage is set to the electrode of the optical resonator 50a to form the electric field E1, the refractive index of the electro-optic crystal in the optical resonator 50a is changed under the action of the electric field E1, so that the optical resonator 50a performs the first filtering process on the collimated light, that is, the optical resonator 50a receives the light with the wavelength λa, the light with the wavelength λb, the light with the wavelength λc and the light with the wavelength λd under the action of the electric field E1, and filters out the light with the wavelength λa and the light with the wavelength λd. When a driving voltage is applied to the electrode of the optical resonator 50b to form an electric field E2, the refractive index of the electro-optic crystal in the optical resonator 50b is changed under the action of the electric field E2, so that the optical resonator 50b performs a second filtering process on the straight light, that is, the optical resonator 50b receives the light with the wavelength λa and the light with the wavelength λd under the action of the electric field E2, and filters out the light with the wavelength λd. In this ideal state, the light with wavelength λd is the output filtered light.

The voltage applied to the electrode of the optical resonator 50a may be the same as or different from the voltage applied to the electrode of the optical resonator 50b, and the voltage applied to the temperature control structure of the optical resonator 50a for forming the current loop may be the same as or different from the voltage applied to the temperature control structure of the optical resonator 50b for forming the current loop.

A fiber collimator 60b for coupling the output filtered light to the fiber output. Specifically, the optical fiber collimator may collimate a plurality of light rays having different propagation directions so that the propagation directions of the plurality of light rays are the same, and the optical fiber collimator may couple the light rays to a certain optical fiber for output, and in the optical filter 11 shown in fig. 18, the optical fiber collimator 60b couples the output filtered light rays to the optical fiber 601b for output.

In the optical filter 11, since the cavity lengths of any two optical resonators among the plurality of optical resonators are different, and the refractive indexes of the electro-optical crystals in the plurality of optical resonators are affected by both the temperature and the electric field, the wavelengths of the light rays filtered out by any two optical resonators among the plurality of optical resonators are not exactly the same, and the wavelengths of the blocked light rays are different. When the plurality of optical resonant cavities align the straight light rays for filtering treatment, more light rays with other wavelengths except the preset wavelength are blocked, and the generated output filtering light rays with the preset wavelength contain less light rays with other wavelengths except the preset wavelength, so that the filtering effect is improved.

However, in the operation of the optical filter 11, the above-mentioned ideal state rarely occurs, and in most cases, the collimated light includes light rays with a plurality of wavelengths, and when the collimated light rays sequentially pass through the plurality of optical resonant cavities 50 along the first direction, each of the plurality of optical resonant cavities 50 sequentially filters the collimated light rays, and the generated first filtered light rays include light rays with predetermined wavelengths but also light rays with wavelengths other than the predetermined wavelengths (also referred to as interference light rays).

Then, referring to fig. 19, an embodiment of the present application provides the optical filter 12, wherein the optical path between the fiber collimator 60a and the fiber collimator 60b further includes: a reflective element 70a.

In the optical filter 12, the optical fiber collimator 60a is configured to collimate the received light (i.e., the input light transmitted by the optical fiber 601 a) to generate collimated light, and sequentially pass the collimated light through the plurality of optical resonators along the first direction. The plurality of optical resonators are specifically used for performing filtering processing on the collimated light rays to generate first filtered light rays containing a preset wavelength. Any two of the plurality of optical resonators 50 are different in cavity length, and each of the plurality of optical resonators 50 is any one of the optical resonators 50 described above.

The reflecting element 70a is configured to reflect the first filtered light to the plurality of optical resonators 50, so that the first filtered light sequentially passes through the plurality of optical resonators 50 along a second direction, and the second direction is opposite to the first direction.

Specifically, the reflecting element 70a includes a reflecting mirror 701a and a reflecting mirror 702a, when an included angle between the reflecting mirror 701a and the reflecting mirror 702a is exactly 90 degrees, the reflecting mirror 701a is configured to receive a first filtered light, the first filtered light reflects on the reflecting mirror 701a for the first time, and the reflecting mirror 701a reflects the first filtered light onto the reflecting mirror 702 a; the first filtered light is then reflected a second time on the mirror 702a, the mirror 702a being configured to reflect the first filtered light to the plurality of optical resonators 50 such that the first filtered light passes through the plurality of optical resonators 50 in a second direction exactly pointing in x-x. Wherein, the angle between the mirror 701a and the mirror 702a may tolerate a process error of 0.5 degrees, for example, the angle between the mirror 701a and the mirror 702a may be 89.5 degrees or more and 90.5 degrees or less, and within the range of the process error of 0.5 degrees, the first filtered light reflected by the reflective element 70a may also be considered to sequentially pass through the plurality of optical resonators 50 in the second direction of x-x.

Alternatively, the reflective element 70a comprises a right angle prism such that a first right angle surface of the right angle prism is configured to receive the first filtered light, the first right angle surface of the right angle prism reflecting the first filtered light to a second right angle surface of the right angle prism, the second right angle surface being configured to reflect the first filtered light reflected by the first right angle surface to the plurality of optical resonators 50 such that the first filtered light sequentially passes through the plurality of optical resonators 50 in a second direction in which x is directed-x. The angle between the first right-angle surface of the right-angle prism and the second right-angle surface of the right-angle prism may tolerate a process error of 0.5 degrees, for example, the angle between the first right-angle surface of the right-angle prism and the second right-angle surface of the right-angle prism may be 89.5 degrees or more and 90.5 degrees or less, and within the range of the process error of 0.5 degrees, the first filtered light reflected by the reflecting element 70a may also be considered to pass through the plurality of optical resonant cavities 50 again in the second direction of x-x.

The plurality of optical resonators 50 are further configured to filter the first filtered light reflected by the reflecting element 70a to generate an output filtered light including light with a predetermined wavelength. Specifically, when the reflection element 70a is configured to reflect the first filtered optical fiber to the plurality of optical resonant cavities 50, so that the first filtered light passes through the optical resonant cavities 50b and 50a again, the optical resonant cavities 50b perform the filtering treatment on the first filtered light, the optical resonant cavities 50a perform the second filtering treatment on the first filtered light to obtain the second filtered light, and compared with the first filtered light, the interference light in the second filtered light is blocked, so that the filtering effect is improved.

For example, referring to fig. 18 or 19, the fiber collimator 60a and the fiber collimator 60b may be replaced with a collimator array including at least 2 fiber collimators, and a first fiber collimator of the 2 fiber collimators for performing the function of the fiber collimator 60 a; the second of the 2 fiber collimators is used to perform the function of fiber collimator 60 b.

Illustratively, referring to fig. 20, another optical filter 13 is provided according to an embodiment of the present application, and the plurality of optical resonators 50 in the optical filter 13 may further include, compared to the optical filter 12: an optical resonator 50c. Then in this optical filter 13, there are 3 optical resonators, the 3 optical resonators are different in cavity length, and 2 optical resonators are any one of the optical resonators 50 described above. More specifically, the difference in cavity length between any two of the three optical resonators is 5um or more. In this optical filter 13, since there are 3 optical resonators, the 3 optical resonators differ in the cavity length, and therefore the wavelengths of light filtered out by the 3 optical resonators are not exactly the same, in which case the number of times of filtering increases to 3 times so that the reflectance requirement of the optical filter 13 for the material used for the reflective film of each optical resonator decreases again.

It should be noted that, the number of optical resonant cavities included in the plurality of optical resonant cavities 50 is not limited in the embodiment of the present application.

When filtering is performed using the optical filter 13 shown in fig. 20, the voltage between the first electrode and the second electrode in the optical resonator 50a is 48.9V (V), the cavity length of the optical resonator 50a is 152um, and the voltage applied by the temperature control structure in the optical resonator 50a to form the current loop is (0V); the intensity of the electric field E formed between the first electrode and the second electrode in the optical resonator 50b is (voltage 18.7V), the cavity length of the optical resonator 50b is 178um, and the voltage applied by the temperature control structure in the optical resonator 50b to form a current loop is (0V); the voltage between the first electrode and the second electrode in the optical resonator 50c is 51.2V, the cavity length of the optical resonator 50c is 186um, and the voltage applied by the temperature control structure in the optical resonator 50c to form the current loop is (0V). Then, when the wavelength of the light received by the optical fiber collimator 60a is between 1525nm and 1570nm and the total wavelength range is 45nm, the output filtered light outputted from the optical fiber collimator 60b is shown with reference to fig. 21, and in fig. 21, the abscissa represents the wavelength (WL in nm) of the output filtered light outputted from the optical fiber collimator 60b, and the ordinate represents the insertion loss (IL in dB) of the output filtered light outputted from the optical fiber collimator 60 b. Wherein the insertion loss (i.e., the energy loss of the light) of the output filtered light with the wavelength of approximately 1541nm is about-42 dB, i.e., the energy of the output filtered light with the wavelength of 1543nm is less than 0.01% of the energy of the input light; the insertion loss of the output filter light with the wavelength of about 1543nm is about-3 dB, namely the energy of the output filter light with the wavelength of 1543nm is more than 63% of the energy of the input light, and the output filter light can be obtained by the optical filter 13; the insertion loss of the output filtered light with a wavelength of approximately 1546nm is approximately-42 dB, i.e. the energy of the output filtered light with a wavelength of 1546nm is less than 0.01% of the energy of the input light. Then, it is considered that the optical filter 13 can filter out the single output filtered light having a wavelength of 1543nm from the input light having a wavelength range of 45nm, and the insertion loss of the single output filtered light having a wavelength of approximately 1543nm can be controlled within 5dB or even 3dB, and the insertion loss of the disturbance light is less than-42 dB.

For example, referring to fig. 22, an embodiment of the present application provides an optical filter 14, in which, in comparison to the optical filter 13, the optical fiber collimator 60a and the optical fiber collimator 60b may be replaced by a dual-fiber collimator 80, in which two optical fibers, respectively, the optical fiber 801 and the optical fiber 802, are included in the dual-fiber collimator 80, and the optical fiber 801 in the dual-fiber collimator may be used to transmit the input light to the plurality of optical resonators 50, and the optical fiber 802 in the dual-fiber collimator may be used to transmit the output filtered light. It should be noted that, in the optical filter 14 shown in fig. 22, if the collimated light is incident into each of the plurality of optical resonators 50 at the incident angle α3, then the first filtered light reflected by the reflecting element 70a is also required to be incident into each of the plurality of optical resonators 50 at the incident angle α3. Thus, in the optical filter shown in fig. 22, each of the reflective films of each of the plurality of optical resonators 50 is parallel to each other, and the bisector of the angle between the first filtered light ray before being reflected by the reflective element 70a and the first filtered light ray after being reflected by the reflective element 70a is exactly parallel to the normal line of the collimated light ray incident on each of the plurality of optical resonators 50.

Alternatively, in this example, the reflecting element 70a may be replaced with a mirror, and the reflecting surface of the mirror is parallel to any one of the reflecting films of each of the optical resonators.

Illustratively, referring to fig. 23, in the optical filter 15 shown in fig. 23, on the basis of the optical filter 12 shown in fig. 23, a reflecting element 70b is further included in the optical path between the optical fiber collimator 60a and the optical fiber collimator 60b, and then, in the optical path of the optical filter 15 shown in fig. 23, the optical fiber collimator 60a and the reflecting element 70b are located on the first side of the plurality of optical resonators 50; the fiber collimator 60b and the reflective element 70a are located on a second side of the plurality of optical resonators 50. And the plurality of optical resonators 50 are exemplified by optical resonator 50a and optical resonator 50b to explain the principle of operation of optical filter 15.

The optical resonators 50a and 50b are the optical resonators 50 shown in fig. 5, but the optical resonators 50a and 50b may be any of the optical resonators 50.

In the optical filter 15, the optical fiber collimator 60a is configured to collimate the received light (i.e., the input light transmitted by the optical fiber 601 a) to generate collimated light, and sequentially pass the collimated light through the optical resonant cavity 50a and the optical resonant cavity 50b along a first direction (i.e., -x pointing in the x direction). An optical resonator 50a for performing a first filtering process on the collimated light; the optical resonator 50b is configured to perform a second filtering process on the collimated light, and generate a first filtered light including a predetermined wavelength.

The reflecting element 70a is configured to reflect the first filtered light to the plurality of optical resonators 50, so that the first filtered light sequentially passes through the optical resonators 50b and the optical resonators 50a along a second direction (i.e., the direction in which x is directed to-x), and the second direction is opposite to the first direction.

The plurality of optical resonators 50 filter the first filtered light reflected by the reflecting element 70a to generate a second filtered light having a predetermined wavelength. Specifically, the optical resonant cavity 50b is configured to perform a first filtering process on the first filtered light; the optical resonator 50a is configured to perform a second filtering process on the first filtered light, so as to generate a second filtered light with a predetermined wavelength.

The reflecting element 70b is configured to reflect the second filtered light to the plurality of optical resonators 50, so that the second filtered light sequentially passes through the optical resonators 50a and the optical resonators 50b along the first direction, that is, the reflecting element 70b reverses the propagation direction of the second filtered light.

The plurality of optical resonators 50 filter the second filtered light reflected by the reflecting element 70b to generate an output filtered light including a predetermined wavelength. An optical resonator 50a for performing a first filtering process on the second filtered light; the optical resonator 50b is configured to perform a second filtering process on the second filtered light, and further generate an output filtered light with a predetermined wavelength.

Then, the fiber collimator 60b is used to couple the output filtered light to the fiber 601b output.

Then, in the optical filter 15 shown in fig. 23, the reflective element 70b is present, where the reflective element 70b reflects the second filtered light to the plurality of optical resonant cavities 50, so that the plurality of optical resonant cavities 50 filter the second filtered light, and therefore the plurality of optical resonant cavities 50 further block the remaining light with other wavelengths to be blocked in the second filtered light, so as to generate the output filtered light with the predetermined wavelength, so as to improve the filtering effect.

Specifically, the reflecting element 70b includes a reflecting mirror 701b and a reflecting mirror 702b, where when an included angle between the reflecting mirror 701b and the reflecting mirror 702b is exactly 90 degrees, the reflecting mirror 701b is configured to receive the second filtered light, the second filtered light reflects the reflecting mirror 701b for the first time, and the reflecting mirror 701b reflects the second filtered light onto the reflecting mirror 702 b; the second filtered light ray then reflects a second time on a mirror 702b, which mirror 702b is configured to reflect the second filtered light ray to the plurality of optical resonators 50 such that the second filtered light ray passes through the plurality of optical resonators 50 in sequence in exactly the first direction in which-x is directed toward x. Wherein, the angle between the mirror 701b and the mirror 702b can tolerate a process error of 0.5 degrees, for example, the angle between the mirror 701b and the mirror 702b can be 89.5 degrees or more and 90.5 degrees or less, and within the range of the process error of 0.5 degrees, the second filtered light passing through the reflective element 70b can also be considered to sequentially pass through the plurality of optical resonators 50 in the first direction of-x pointing x.

Alternatively, the reflecting element 70b includes a right angle prism including a third right angle surface and a fourth right angle surface, and then the third right angle surface of the right angle prism is configured to receive the second filtered light, and the third right angle surface of the right angle prism reflects the second filtered light to the fourth right angle surface of the right angle prism; the fourth right angle surface is configured to reflect the second filtered light reflected by the third right angle surface to the plurality of optical resonators 50, so that the second filtered light sequentially passes through the plurality of optical resonators 50 along the first direction in which-x is directed to x. The angle between the third right angle surface of the right angle prism and the fourth right angle surface of the right angle prism may tolerate a process error of 0.5 degrees, for example, the angle between the third right angle surface of the right angle prism and the fourth right angle surface of the right angle prism may be 89.5 degrees or more and 90.5 degrees or less, and within the range of the process error of 0.5 degrees, the second filtered light passing through the reflective element 70b may also be considered to pass through the plurality of optical resonant cavities 50 again in the first direction of-x pointing to x.

When the optical filter 15 shown in fig. 23 is used for filtering, the intensity of the electric field E formed between the first electrode and the second electrode in the optical resonator 50a is (voltage 0 to 60V), the cavity length of the optical resonator 50a is 89um, and the voltage applied by the temperature control structure in the optical resonator 50a for forming a current loop is (voltage 0 to 30V); the intensity of the electric field E formed between the first electrode and the second electrode in the optical resonator 50b is (voltage 0 to 60V), the cavity length of the optical resonator 50b is 99um, and the voltage applied by the temperature control structure in the optical resonator 50b for forming the current loop is (voltage 0 to 30V).

For example, if the optical resonator 50a filters the input light having a wavelength of 1524nm to 1572nm and a total wavelength range of 48nm, a simulation of the output filtered light output from the optical resonator 50a is shown with reference to fig. 24, in which the abscissa represents the wavelength (WL in nm) of the output filtered light output from the optical collimator 60b and the ordinate represents the Insertion Loss (IL in dB) of the output filtered light output from the optical collimator 60b in fig. 24. The free spectral range of the filtered light outputted by the optical resonator 50a is 660GHz, the insertion loss of the peak of the outputted filtered light is 0dB, and when the absorption of the material in the optical resonator 50a is ignored, the theoretical simulation insertion loss is close to 0dB, and the insertion loss of the trough of the outputted filtered light is-60 dB.

For example, if the optical resonator 50b filters the input light having a wavelength of 1524nm to 1572nm and a total wavelength range of 48nm, a simulation of the filtered light output from the optical resonator 50a is shown with reference to fig. 25, in which fig. 25, the abscissa represents the Wavelength (WL) of the output filtered light output from the optical collimator 60b, and the ordinate represents the Insertion Loss (IL) of the output filtered light output from the optical collimator 60 b. Wherein, the free spectral range of the output filtered light outputted by the optical resonant cavity 50b is 600GHz, the insertion loss of the peak of the output filtered light is 0dB, and when the absorption of the material in the optical resonant cavity 50b is ignored, the theoretical simulation insertion loss is close to 0dB, and the insertion loss of the trough of the output filtered light is-60 dB.

Then, in the optical filter 15, the wavelength of the light received by the optical fiber collimator 60a is between 1524nm and 1572nm, the total wavelength range is 48nm of the input light, the output filtered light outputted by the optical fiber collimator 60b is shown with reference to fig. 26, and in fig. 26, the abscissa indicates the wavelength (WL in nm) of the output filtered light outputted by the optical fiber collimator 60b, and the ordinate indicates the Insertion Loss (IL in dB) of the output filtered light outputted by the optical fiber collimator 60 b. In the optical filter 15, the output filtered light beam output from the optical collimator 60b corresponds to the interference between the output filtered light beam output from the optical resonator 50a and the output filtered light beam output from the optical resonator 50 b. The insertion loss (i.e., the energy loss of the light) of the output filtered light with the wavelength of approximately 1548nm in the output filtered light in fig. 26 is about 0dB, that is, the energy of the output filtered light with the wavelength of approximately 1548nm is equal to the energy of the input light, which is the output filtered light that can be obtained by the optical filter 15; the insertion loss of the output filtered light with the wavelength of about 1543nm is about-30 dB; the insertion loss of the output filtered light with the wavelength of approximately 1553nm is approximately-30 dB. Then, it is considered that the optical filter 15 can filter out the single output filtered light having a wavelength of approximately 1548nm from the input light having a wavelength range of 48nm, and the insertion loss of the single output filtered light having a wavelength of approximately 1548nm can be controlled within 5dB or even 3dB, and the insertion loss of the disturbing light is less than-26 dB.

As an example, referring to fig. 27, another optical filter 16 is provided in the embodiment of the present application, and the optical filter 16 is different from the optical filter 15 described above in that the specific structures of the optical resonant cavity 50a and the optical resonant cavity 50b in the optical filter 15 are shown in fig. 5, and the specific structures of the optical resonant cavity 50a and the optical resonant cavity 50b in the optical filter 16 are shown in fig. 8, and the working principle thereof is referred to the working principle of the optical filter 15 and is not described herein.

Although the application has been described in connection with specific features and embodiments thereof, it will be apparent that various modifications and combinations can be made without departing from the spirit and scope of the application. Accordingly, the specification and drawings are merely exemplary illustrations of the present application as defined in the appended claims and are considered to cover any and all modifications, variations, combinations, or equivalents that fall within the scope of the application. It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

Claims

1. An optical resonator, comprising:

an electro-optic crystal;

a first electrode and a second electrode, wherein the first electrode and the second electrode are respectively arranged at two sides of the electro-optic crystal along the propagation direction of the electro-optic crystal; the first electrode and the second electrode are used for applying an electric field to the electro-optical crystal, the electric field is used for adjusting the refractive index of the electro-optical crystal, and the electric field has a component parallel to the propagation direction;

a first reflective film and a second reflective film, wherein the first reflective film is disposed on a side of the first electrode away from the electro-optic crystal, and the second reflective film is disposed on a side of the second electrode away from the electro-optic crystal;

a temperature control structure, wherein the temperature control structure applies a temperature to the electro-optic crystal to adjust a refractive index of the electro-optic crystal;

the first reflecting film is used for transmitting input light rays in the propagation direction and transmitting the transmitted light rays to the electro-optical crystal through the first electrode;

the electro-optical crystal is used for transmitting the light transmitted by the first reflecting film to the second reflecting film through the second electrode under the action of the temperature and the electric field and with a preset refractive index;

The second reflecting film is used for outputting light rays with a preset wavelength in the light rays transmitted by the electro-optical crystal and reflecting the light rays with other wavelengths except the preset wavelength to the electro-optical crystal through the second electrode;

the electro-optical crystal is further used for transmitting the light reflected by the second reflecting film to the first reflecting film through the first electrode at the preset refractive index;

the first reflecting film is also used for reflecting the light transmitted by the electro-optical crystal to the electro-optical crystal through the first electrode.

2. The optical resonator according to claim 1, characterized in that,

the temperature control structure is arranged on one side of the first reflecting film far away from the electro-optic crystal; and/or the temperature control structure is arranged on one side of the second reflecting film far away from the electro-optical crystal.

3. The optical resonator according to claim 1, characterized in that,

the electro-optic crystal comprises a light-transmitting area and a non-light-transmitting area;

the first electrode and the second electrode are respectively arranged at two sides of a light transmission area of the electro-optic crystal along the propagation direction of the electro-optic crystal;

the temperature control structure is arranged on one side or two sides of the non-light-transmitting area.

4. The optical resonator according to claim 1, characterized in that,

the temperature control structure is arranged on one side of the electro-optic crystal along the direction parallel to the propagation direction, and/or the temperature control structure is arranged on the other side of the electro-optic crystal along the direction parallel to the propagation direction.

5. The optical resonator according to any of claims 1-4, wherein the temperature-controlled structure comprises a light-transmissive resistive film.

6. The optical resonator according to claim 5, wherein the resistive film material comprises: indium tin oxide, ITO.

7. An optical resonator according to any of claims 1-6, characterized in that,

the material of the electro-optic crystal comprises any one of the following materials: lithium niobate, potassium niobate tantalate, lanthanum-doped lead zirconate titanate, lead magnesium niobate-lead titanate.

8. An optical resonator according to any of claims 1-7, characterized in that,

in the propagation direction, the distance between the first reflecting film and the second reflecting film is the cavity length of the optical resonant cavity; the cavity length is greater than or equal to 50 microns and less than or equal to 300 microns.

9. An optical resonator according to any of claims 1-8, characterized in that,

The material of the first electrode includes: indium tin oxide, ITO;

the material of the second electrode includes: indium tin oxide, ITO.

10. An optical filter, comprising: a first optical fiber collimator, a second optical fiber collimator, and a plurality of optical resonators as claimed in any one of claims 1 to 9 disposed on an optical path between the first optical fiber collimator and the second optical fiber collimator;

the first optical fiber collimator is used for carrying out collimation treatment on received light rays to generate collimated light rays, and the collimated light rays sequentially pass through the plurality of optical resonant cavities along a first direction;

the plurality of optical resonant cavities are used for carrying out filtering treatment on the collimated light rays and generating output filtering light rays with preset wavelengths; any two optical resonant cavities in the at least one optical resonant cavity have different cavity lengths;

the second fiber collimator is used for coupling the output filtered light to a fiber output.

11. The optical filter of claim 10, wherein the optical path between the first fiber collimator and the second fiber collimator further comprises: a first reflective element;

the plurality of optical resonant cavities are specifically used for performing filtering treatment on the collimated light rays to generate first filtering light rays with preset wavelengths;

The first reflecting element is configured to reflect the first filtered light to the plurality of optical resonant cavities, so that the first filtered light sequentially passes through the plurality of optical resonant cavities along a second direction, and the second direction is opposite to the first direction;

the plurality of optical resonant cavities are further configured to perform filtering processing on the first filtered light reflected by the first reflecting element, and generate output filtered light including the predetermined wavelength.

12. The optical filter of claim 11, further comprising a second reflective element in the optical path between the first fiber collimator and the second fiber collimator;

the plurality of optical resonant cavities are specifically configured to perform filtering processing on the first filtered light reflected by the first reflecting element, so as to generate a second filtered light containing the predetermined wavelength;

the second reflecting element is configured to reflect the second filtered light to the plurality of optical resonant cavities, so that the second filtered light sequentially passes through the plurality of optical resonant cavities along the first direction;

the plurality of optical resonant cavities are further configured to perform filtering processing on the second filtered light reflected by the second reflecting element, so as to generate output filtered light containing the predetermined wavelength.

13. An optical filter according to claim 11 or 12, characterized in that,

the first reflecting element comprises a first reflecting mirror and a second reflecting mirror;

the first reflector is used for receiving the first filtered light and reflecting the first filtered light to the second reflector;

the second reflector is configured to reflect the first filtered light reflected by the first reflector to the plurality of optical resonant cavities, where an included angle between the first reflector and the second reflector is greater than or equal to 89.5 degrees and less than or equal to 90.5 degrees.

14. An optical filter according to claim 11 or 12, characterized in that,

the first reflecting element comprises a first right angle prism; the first right angle prism comprises a first right angle surface and a second right angle surface;

the first right-angle surface is used for receiving the first filtered light and reflecting the first filtered light to the second right-angle surface;

the second right angle surface is configured to reflect the first filtered light reflected by the first right angle surface to the plurality of optical resonant cavities, where an included angle between the first right angle surface and the second right angle surface is greater than or equal to 89.5 degrees and less than or equal to 90.5 degrees.

15. The optical filter of claim 12, wherein the filter is configured to filter the light,

the second reflecting element comprises a third reflecting mirror and a fourth reflecting mirror;

the third reflector is used for receiving the second filtered light and reflecting the second filtered light to the fourth reflector;

the fourth reflector is configured to reflect the second filtered light reflected by the third reflector to the plurality of optical resonant cavities, where an included angle between the third reflector and the fourth reflector is greater than or equal to 89.5 degrees and less than or equal to 90.5 degrees.

16. The optical filter of claim 12, wherein the filter is configured to filter the light,

the second reflecting element comprises a second right angle prism, and the second right angle prism comprises a third right angle surface and a fourth right angle surface;

the third right-angle surface is used for receiving the second filtered light and reflecting the second filtered light to the fourth right-angle surface;

the fourth right angle surface is configured to reflect the second filtered light reflected by the third right angle surface to the plurality of optical resonant cavities, where an included angle between the third right angle surface and the fourth right angle surface is greater than or equal to 89.5 degrees and less than or equal to 90.5 degrees.

17. The optical filter of any of claims 10-16, wherein any two of the plurality of optical resonators have a difference in cavity length of 5 microns or greater.