A tunable optical filter

Abstract

The application discloses a tunable optical filter, which is provided with a fiber pigtail, a mirror, a beam expander, a collimating lens, a light splitting element and a mirror group with a reflecting surface along an optical path. The fiber pigtail has at least three fiber ends, one of which is an incident fiber end and the others are outgoing fiber ends. The extension of the working range of the tunable optical filter is realized by adjusting the distance between the outgoing fiber ends so that the outgoing fibers in different outgoing fiber ends receive different wave optical light in the output optical path. In particular, the mirror group with the reflecting surface contains a semi-transparent half-reflection film and a full-reflection film, and by adjusting the angle of the mirror group with the reflecting surface in different dimensions, the optical signals of different wavelengths are simultaneously received by different outgoing fibers quickly and efficiently.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of optical application, specifically to the technical field of optical filter, and relates to a tunable optical filter. BACKGROUND

[0002] The tunable optical filter is a wavelength selection filter device used in the field of optics, and is commonly used in the fields of optical communication and optical sensing. The method based on a diffraction grating is commonly used due to its narrow filter bandwidth and high stability. However, the working wavelength tuning range of the optical filter is related to the deflection angle of an active angle deflection element. The maximum deflection angle of a commonly used angle deflection element, micro electro mechanical system (MEMS), cannot be made very large due to process reasons, which makes it difficult to expand the working range. In addition, under a large deflection angle deflection element, the overall optical filter structure size will also be large to adapt to the demand of a large working range, which also leads to a significant increase in cost, which is contrary to the goal of product miniaturization and low cost.

[0003] The existing tunable optical filter structure is compact, and a lens is used for beam expansion, so that the light spot size incident on the grating is uniform under different working angles of the MEMS, and the consistency of the filter characteristics within the working wavelength is realized. However, the working range of the optical filter is limited by the deflection angle of the MEMS, and the wavelength range cannot be expanded. SUMMARY

[0004] In order to overcome the above problems, the present application provides a tunable optical filter, which is provided with a fiber pigtail, a mirror, a beam expander, a collimating lens, a light splitting element and a mirror group with a reflecting surface along an optical path. The fiber pigtail has at least three fiber ends, one of which is an incident fiber end and the others are outgoing fiber ends. By adjusting the distance between the outgoing fiber ends, the outgoing fiber in different outgoing fiber ends receives light of different wavelengths in the output optical path, and the working range of the tunable optical filter is expanded. In particular, the mirror group with a reflecting surface contains a semi-transparent half-mirror and a full mirror. By adjusting the angle of the mirror group with a reflecting surface in different dimensions, different wavelength optical signals are simultaneously received by different outgoing fibers, thereby completing the application.

[0005] Specifically, the present application aims to provide the following aspects:

[0006] In a first aspect, a tunable optical filter is provided, which is provided with a fiber pigtail, a mirror, a beam expander, a collimating lens, a light splitting element and a mirror group with a reflecting surface along an optical path. The fiber pigtail has at least three fiber ends, one of which is an incident fiber end and the others are outgoing fiber ends.

[0007] Wherein, the incident light is sequentially emitted from the optical fiber Pigtail, the mirror, the beam expander lens, the collimator lens, the light splitting element, the mirror group with reflecting surface, the light splitting element, the collimator lens, the beam expander lens and the mirror, and the different exit optical fiber ends of the optical fiber Pigtail emit light at the same time.

[0008] Wherein, the mirror group with reflecting surface is a total reflection mirror; and the distribution of the exit optical fiber end is parallel to the light splitting direction.

[0009] Wherein, the mirror group with reflecting surface contains a half-transmission half-reflection film and a total reflection film.

[0010] Optionally, the mirror group with reflecting surface contains a half-transmission half-reflection mirror and a total reflection mirror, and the half-transmission half-reflection mirror is arranged between the light splitting element and the total reflection mirror. One side of the half-transmission half-reflection mirror is an incident surface, and a half-transmission half-reflection film is coated on the incident surface; the other side is an exit surface, and an anti-reflection film is coated on the exit surface.

[0011] Optionally, the mirror group with reflecting surface is a prism, one side of the prism is an incident surface, and a half-transmission half-reflection film is coated on the incident surface; the other side is an exit surface, and a total reflection film is coated on the exit surface.

[0012] Wherein, the distribution of the exit optical fiber end is staggered in the vertical direction of the light splitting direction.

[0013] Wherein, the distance between the exit optical fiber ends is adjustable.

[0014] The present application has the beneficial effects, including:

[0015] (1) The tunable optical filter provided by the present application uses the optical fiber Pigtail containing a plurality of exit optical fiber ends to achieve the purpose of receiving different wavelength ranges by different exit optical fiber ends, solves the wavelength range limitation of the traditional tunable optical filter, and realizes the significant increase of the working wavelength range without obvious increase in cost and structure size.

[0016] (2) The tunable optical filter provided by the present application contains a half-transmission half-reflection film and a total reflection film on the mirror group with reflecting surface, and by adjusting the angle of the mirror group with reflecting surface in different dimensions, different wavelength optical signals are quickly and efficiently received by different exit optical fiber ends at the same time.

[0017] (3) The tunable optical filter provided by the present application has reasonable structure design, fewer components and compact structure. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 The structure schematic diagram of the tunable optical filter according to a preferred embodiment of the present application is shown;

[0019] Figure 2 shows Figure 1 schematic diagram showing a first exit fiber end and a second exit fiber end on a fiber pigtail receiving a middle splitting light spot;

[0020] Figure 3 shows a schematic diagram of a tunable optical filter structure according to a preferred embodiment of the present application;

[0021] Figure 4 shows Figure 3 schematic diagram showing a first exit fiber end and a second exit fiber end on a fiber pigtail receiving a middle splitting light spot;

[0022] Figure 5 shows a schematic diagram of a tunable optical filter structure according to a preferred embodiment of the present application;

[0023] Figure 6 shows Figure 5 schematic diagram showing a first exit fiber end and a second exit fiber end on a fiber pigtail receiving a middle splitting light spot;

[0024] Figure 7 shows a schematic diagram of a tunable optical filter structure according to a preferred embodiment of the present application.

[0025] BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 1 - fiber pigtail;

[0027] 101 - incident fiber end;

[0028] 102 - first exit fiber end;

[0029] 103 - second exit fiber end;

[0030] 111 - first splitting light spot;

[0031] 112 - second splitting light spot;

[0032] 113 - splitting light spot;

[0033] 2 - mirror;

[0034] 3 - beam expander lens;

[0035] 4 - collimating lens;

[0036] 5 - splitting element;

[0037] 6 - total reflection mirror;

[0038] 7 - half-mirror;

[0039] 8 - prism;

[0040] 801 - half-transmission half-reflection film;

[0041] 802 - full-reflection film;

[0042] 9 - second optical fiber pigtail;

[0043] 901 - third exit optical fiber end. DETAILED DESCRIPTION

[0044] The present application will be further described by the following drawings and examples. The features and advantages of the present application will become more apparent from the detailed description, when taken in conjunction with the accompanying drawings, in which:

[0045] The term "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any implementation described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other implementations. Unless specifically indicated otherwise, the drawings are not necessarily to scale.

[0046] The present application aims to provide a tunable optical filter, which is provided with an optical fiber pigtail 1, a mirror 2, a beam expander 3, a collimator 4, a light splitting element 5 and a mirror group with a reflecting surface along an optical path, the optical fiber pigtail 1 has at least three optical fiber ends, one of which is an incident optical fiber end, and the rest are exit optical fiber ends. By adjusting the distance between the exit optical fiber ends, the different exit optical fiber ends receive different wavelength light, and the working range of the tunable optical filter is expanded.

[0047] Further, the optical fiber pigtail 1 is preferably a collimator, which realizes the collimation of the optical path transmission.

[0048] According to the present application, based on the fact that the optical fiber pigtail 1 has more than three optical fiber ends, one of which is an incident optical fiber end, and the rest are exit optical fiber ends, by adjusting the distance between the exit optical fiber ends, the relative difference of the wavelengths of the light output by different exit optical fiber ends is adjusted, the purpose of receiving different wavelength ranges by different exit optical fiber ends is achieved, the working wavelength range limitation of the traditional tunable optical filter is solved, and the working wavelength range is significantly increased without obvious increase in cost and structure size.

[0049] In the present application, the incident light from the fiber Pigtail 1 such as collimator outputs a multi-wavelength parallel light beam, which is incident on the mirror 2, and after being reflected by the mirror 2, is directed to the beam expander lens 3, where the light beam is expanded, and then is directed to the collimating lens 4, where the light beam is collimated, and the collimated parallel light beam is directed to the light splitting element 5, which splits the light beam into single-wavelength light signals with different diffraction angles, and the single-wavelength light signals with different angles are reflected by the mirror group with a reflecting surface, and the reflected single-wavelength light signals with different angles are partially returned to the beam expander lens 3 along the original path, and the light path of the light beam through the beam expander lens 3 is reflected on the mirror 2, and the light is emitted from the fiber end of the fiber Pigtail 1 such as collimator, and the rest is reflected into the outside and causes loss.

[0050] In the present application, the light beam returned along the original path is emitted from the beam expander lens 3, and according to the principle of reversible light path, the light spot formed on the fiber end of the fiber Pigtail 1 such as collimator is restored to the original size in the light splitting longitudinal axis direction, and due to the light splitting effect of the light splitting element 5, the size of the light spot in the light splitting transverse axis direction is significantly increased, and the light spot in the light splitting direction is distributed according to the wavelength, and the different wavelengths of the light signal can be received by the emitting fiber at different positions of the light splitting light spot.

[0051] Further, due to the deflection angle of the mirror 2 and the size of the light splitting light spot in the light splitting direction received by the emitting fiber in the fiber end, the wavelength received by the emitting fiber in the fiber end is limited. By providing two or more fiber ends in one fiber Pigtail 1, different emitting fiber ends can receive different wavelengths of light signals, and the working range of the tunable optical filter can be expanded.

[0052] Of course, in most cases, the size of the light splitting light spot received by one fiber Pigtail 1 in the light splitting direction is larger than the diameter of the fiber Pigtail 1, and two or more emitting fibers cannot be reasonably arranged in one fiber Pigtail 1, and in this case, a second fiber Pigtail 1 or even more fiber Pigtails 1 can be provided instead of the second or even multiple emitting fibers. At this time, the second fiber Pigtail 1 and the more fiber Pigtails 1 need to be parallel to the fiber Pigtail 1 in the light splitting direction, and the emitting fibers in them also need to be parallel in the light splitting direction. At this time, by adjusting the spacing between the emitting fibers, the emitting fibers in the multiple emitting fiber ends can simultaneously receive the oversized emitting light splitting light spot.

[0053] In the present application, the fiber Pigtail 1 distributes the emitting fibers according to the light splitting direction, and the returning light splitting light spot of the mirror group with a reflecting surface is received by the emitting fibers in multiple emitting fiber ends, but the wavelengths received by the multiple emitting fibers are different.

[0054] In the present invention, the reflector 2 is a MEMS deflection mirror, or a reflector with the same function as the MEMS deflection mirror; the collimating lens 4 is preferably a beam expanding collimating lens, which simultaneously realizes the collimation and expansion of the light beam, and the beam expanding lens 3 and the collimating lens 4 are confocal; the spectrometer element 5 is a diffraction grating; the mirror group with a reflective surface is coated with a total reflection film 802.

[0055] According to the present invention, the light beam expanded by the collimating lens 4 is incident on the beam splitting element 5 at an angle of approximately 45° with respect to the horizontal direction.

[0056] In one embodiment, Figure 1 As shown, the optical fiber Pigtail 1 is a multi-fiber collimator, which contains three optical fibers, one of which is an incident optical fiber end 101, and the other two are a first output optical fiber end 102 and a second output optical fiber end 103. The mirror assembly with a reflective surface is a total reflection mirror 6, and the total reflection mirror 6 is coated with a total reflection film 802. The incident light is emitted from the incident optical fiber end 101 through the reflector 2, the beam expander lens 3, the collimating lens 4, the beam splitter 5, the total reflection mirror 6, the beam splitter 5, the collimating lens 4, the beam expander lens 3, and the reflector 2 in sequence, and is emitted from the first output optical fiber end 102 and the second output optical fiber end 103.

[0057] Furthermore, if Figure 2 As shown, the return beam splitting spot 113 from the total reflection mirror 6 can be received simultaneously by the first output fiber end 102 and the second output fiber end 103, but the wavelengths received by the two output fibers are different. Specifically, due to the angle limitation of the reflector 2, the output wavelength range of the first output fiber end 102 is between λ1 and λx, while the output wavelength range of the second output fiber end 103 is between λx and λn. Therefore, the first output fiber end 102 and the second output fiber end 103 work together to meet the working range requirements of λ1 to λn.

[0058] Furthermore, if Figure 3 As shown, Figure 1 In the multi-fiber collimator, the first output fiber end 102 or the second output fiber end 103 is replaced by a second fiber Pigtail 9. The second fiber Pigtail 9 is a second collimator to prevent the multi-fiber collimator from receiving a large size of the splitting light spot in the splitting direction, which may result in the inability to output all wavelengths.

[0059] In this case, if Figure 4 As shown, the output wavelength range of the first output fiber end 102 is between λ1 and λx, and the output wavelength range of the third output fiber end 901 of the second collimator is between λx and λn. The first output fiber end 102 and the third output fiber end 901 work together to meet the working range requirements of λ1 to λn.

[0060] Furthermore, when the mirror assembly with a reflective surface is a total reflection mirror 6, the arrangement direction of the output fiber ends on the optical fiber Pigtail 1 is parallel to the splitting direction. At this time, a reasonable spacing distance between the output fibers enables different output fibers to simultaneously receive optical signals of different wavelengths, thereby expanding the working range.

[0061] The inventors discovered that while the operating range of the tunable optical filter can be expanded by adjusting the distance between the output fiber ends so that different output fiber ends receive light of different wavelengths in the output optical path, the adjustment of the output fiber end distance is limited, particularly when adjusting the distance between multiple output fiber ends within a single optical fiber Pigtail 1. This makes it difficult for multiple output fiber ends to receive all wavelengths. When the reflective mirror assembly includes both a semi-transmissive and semi-reflective film 801 and a fully reflective film 802, by adjusting the angles of the reflective mirror assembly in different dimensions, optical signals of different wavelengths can be quickly and efficiently received simultaneously by the output fibers within different output fiber ends.

[0062] In one embodiment, Figure 5 As shown, the optical fiber pigtail 1 is a multi-fiber collimator. The mirror assembly with a reflective surface is a semi-transparent mirror 7 and a total reflection mirror 6. The semi-transparent mirror 7 is arranged between the beam splitter 5 and the total reflection mirror 6. That is, a multi-fiber collimator, a reflector 2, a beam expander lens 3, a collimating lens 4, a beam splitter 5, a semi-transparent mirror 7, and a total reflection mirror 6 are arranged along the optical path. The multi-fiber collimator has three fiber ends, one of which is an input fiber end 101, and the other two are a first output fiber end 102 and a second output fiber end 103.

[0063] Furthermore, a semi-transparent mirror 7 is provided above the total reflection mirror 6, between the beam splitting element 5 and the total reflection mirror 6. One side of the semi-transparent mirror 7 is an incident surface coated with a semi-transparent and semi-reflective film 801, and the other side is an exit surface coated with an anti-reflection film. The total reflection mirror 6 is coated with a total reflection film 802. The semi-transparent mirror 7 and the total reflection mirror 6 are adjustable in both the beam splitting direction and the vertical direction. By adjusting the pitch and swing angles of the semi-transparent mirror 7 and the total reflection mirror 6, the output optical fibers within the multiple output optical fibers can each receive the desired wavelength.

[0064] Among them, the incident light enters through the incident fiber end 101 of the multi-fiber collimator and is incident on the reflector 2. After passing through the reflector 2, the light beam is incident on the collimating and expanding system composed of the beam expander lens 3 and the collimating lens 4 and is emitted. The expanded light beam is incident on the spectrometer 5 at an angle of about 45°, and is split at the spectrometer 5. The single-wavelength light signals at different angles after splitting are incident on the incident surface of the semi-transparent and semi-reflective mirror 7.

[0065] Furthermore, a portion of the single-wavelength optical signals at different angles after splitting is reflected at the semi-transparent and semi-reflective film 801, and the reflected portion of the single-wavelength optical signals at different angles returns along the original path, and the rest is reflected into the outside world and causes loss; while the other portion is emitted from the exit surface of the semi-transparent and semi-reflective mirror 7 to the total reflection mirror 6 and reflected, and the reflected portion of the single-wavelength optical signals at different angles passes through the incident surface of the semi-transparent and semi-reflective mirror 7 again and returns along the original path, and part of it is reflected into the outside world and causes loss.

[0066] Furthermore, when the above-mentioned light beam returning along the original path is emitted from the beam expander lens 3, the splitting light spot formed by the light beam on the output fiber end of the multi-fiber collimator is restored to its original size in the longitudinal direction of the splitting light, and its size in the transverse direction of the splitting light is significantly increased. The splitting light spot is distributed according to the wavelength in the splitting direction. In this scheme, due to the different return paths of the semi-transparent and semi-reflective mirror 7 and the total reflection mirror 6, two splitting light spots with different positions appear accordingly.

[0067] Furthermore, due to the limitation of the deflection angle of the reflector 2 and the size of the splitting spot received by the multi-fiber collimator in the splitting direction, the wavelength that the output fiber in each output fiber end can receive is limited. Figure 6 As shown, the first splitting light spot 111 represents the return light of the semi-transparent and semi-reflective mirror 7, and the second splitting light spot 112 represents the return light of the total reflection mirror 6. Due to the splitting reason, the horizontal axis size of the two splitting light spots is much larger than the vertical axis size. Since the angles of the semi-transparent and semi-reflective mirror 7 and the total reflection mirror 6 in different dimensions are different, the positions of the two splitting light spots in the vertical direction and the splitting direction of the multi-fiber collimator are also different. At this time, the angles of each dimension of the semi-transparent and semi-reflective mirror 7 and the total reflection mirror 6 are coupled as needed, so that the first output fiber end 102 and the second output fiber end 103 respectively receive the required wavelengths.

[0068] Figure 6 As shown in the figure, the first output fiber end 102 receives the first splitting light spot 111 with a wavelength range of λ1 to λx returned by the semi-transparent and semi-reflective mirror 7, while the second output fiber end 103 receives the second splitting light spot 112 with a wavelength range of λx to λn returned by the total reflection mirror 6. The first output fiber end 102 and the second output fiber end 103 work together to meet the working range requirements of λ1 to λn.

[0069] In the present invention, the transmittance of the semi-transparent and semi-reflective film 801 at each wavelength can be set according to actual needs and specific coating capabilities. In addition, the semi-transparent and semi-reflective film 801 can be replaced by a bandpass and bandstop film to reduce coupling loss.

[0070] According to the present invention, in the tunable optical filter including the semi-transparent and semi-reflective film 801 , the arrangement of the output fiber ends in the optical fiber Pigtail 1 needs to be staggered in a direction perpendicular to the light splitting direction to prevent crosstalk.

[0071] In the present application, as shown in Figure 7 The sampling prism 8 replaces the two half-transmission half-reflection mirrors 7 and the reflection mirror 6. One side of the prism 8 is an incident surface, which is coated with a half-transmission half-reflection film 801, and the other side is an exit surface, which is coated with a full reflection film 802. The half-transmission half-reflection film 801 and the full reflection film 802 are machined into different angles according to the requirements in the pitch angle and the yaw angle, which to some extent reduces the coupling steps and difficulty, and makes the structure of the tunable optical filter more compact.

[0072] In the description of the present application, it should be noted that the terms "upper", "lower", "left", "right", "inner", "outer", "front", "back" and the like indicate the orientation or positional relationship based on the working state of the present application, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", "fourth" are only for the purpose of description, and cannot be understood as indicating or implying relative importance.

[0073] The present application has been described in detail above in conjunction with the preferred embodiments and exemplary examples. However, it should be stated that these specific embodiments are only illustrative explanations of the present application, and do not constitute any limitation on the protection scope of the present application. Various improvements, equivalent replacements or modifications can be made to the technical content and embodiments of the present application without departing from the spirit and protection scope of the present application, which all fall within the protection scope of the present application. The protection scope of the present application is subject to the appended claims.

Claims

1. A tunable optical filter, characterized by, A fiber pigtail (1), a mirror (2), a beam expander (3), a collimator (4), a beam splitter (5) and a mirror group with reflecting surface are arranged along the light path, the fiber pigtail (1) has at least three fiber ends, one of which is an incident fiber end, and the rest are all exit fiber ends, the exit fiber ends are a first exit fiber end (102) and a second exit fiber end (103) respectively; The mirror group with reflecting surface contains a half-transmission half-reflection film (801) and a full-reflection film (802); The mirror group with reflecting surface contains a half-transmission half-reflection mirror (7) and a full-reflection mirror (6), the half-transmission half-reflection mirror (7) is arranged between the beam splitter (5) and the full-reflection mirror (6); The exit fiber ends are staggered in the vertical direction of the splitting direction; Among them, The first exit fiber end (102) receives the first split light spot (111) returned by the half-transmission half-reflection mirror (7), and the second exit fiber end (103) receives the second split light spot (112) returned by the full-reflection mirror (6); By adjusting the pitch angle and swing angle of the half-transmission half-reflection mirror (7) and the full-reflection mirror (6), the first exit fiber end (102) and the second exit fiber end (103) receive the required wavelengths respectively.

2. The tunable optical filter of claim 1, wherein, One side of the half-transmission half-reflection mirror (7) is an incident surface, the incident surface is coated with a half-transmission half-reflection film (801), the other side is an exit surface, and the exit surface is coated with an anti-reflection film.

3. The tunable optical filter of claim 1, wherein, The mirror group with reflecting surface is a prism (8), one side of the prism (8) is an incident surface, the incident surface is coated with a half-transmission half-reflection film (801), the other side is an exit surface, and the exit surface is coated with a full-reflection film (802).

Images