CN111443431A - WDM demultiplexer based on thin film interference filter - Google Patents
WDM demultiplexer based on thin film interference filter Download PDFInfo
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- CN111443431A CN111443431A CN202010280031.2A CN202010280031A CN111443431A CN 111443431 A CN111443431 A CN 111443431A CN 202010280031 A CN202010280031 A CN 202010280031A CN 111443431 A CN111443431 A CN 111443431A
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- prism
- stage
- demultiplexer
- light beam
- film interference
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- G—PHYSICS
- G02—OPTICS
- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/24—Coupling light guides
- G02B6/26—Optical coupling means
- G02B6/28—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals
- G02B6/293—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means
- G02B6/29346—Optical coupling means having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals with wavelength selective means operating by wave or beam interference
- G02B6/29361—Interference filters, e.g. multilayer coatings, thin film filters, dichroic splitters or mirrors based on multilayers, WDM filters
- G02B6/29362—Serial cascade of filters or filtering operations, e.g. for a large number of channels
Abstract
The invention discloses a WDM demultiplexer based on a thin film interference filter, which comprises a front-stage demultiplexer and a rear-stage demultiplexer, wherein the front-stage demultiplexer is arranged in front of a light beam incident port of the rear-stage demultiplexer, an incident light beam is divided into an upper light beam and a lower light beam by the front-stage demultiplexer, the upper light beam and the lower light beam are respectively loaded with a first half of light wave and a second half of light wave, an upper space and a lower space exist when the upper light wave and the lower light wave are emitted in parallel, the rear-stage demultiplexer is used for re-splitting the incident upper light wave and the incident lower light wave, the extendibility of all directions of a three-dimensional space is fully utilized, an optical demultiplexer (DeMUX) can be made to be more compact, meanwhile, the optical paths of certain channels are relatively shortened, the devices are convenient to couple, and the fabrication of.
Description
Technical Field
The invention relates to the technical field of passive devices of physical optics and optical fiber communication, in particular to a WDM demultiplexer based on a thin film interference filter.
Background
The Wavelength Division Multiplexing (WDM) technology has been widely used in optical fiber transmission systems and optical network systems, and uses an optical fiber to transmit a plurality of optical carriers with different wavelengths, making full use of the optical fiber bandwidth, so that the information amount transmitted by the optical fiber is multiplied, thereby greatly reducing the cost of optical fiber transmission; as far as optical wavelength demultiplexers are concerned, the most mature at present are demultiplexers based on thin film interference filters (TFF). Fig. 1 is a typical structure and an optical path schematic diagram of an incident light as a collimated light of a conventional four-wave WDM demultiplexer (DeMUX) based on a thin film interference filter, and fig. 2 is a typical structure and an optical path schematic diagram of an incident light as a collimated light of a conventional eight-wave WDM demultiplexer (DeMUX) based on a thin film interference filter, the entire structure of the optical demultiplexer is composed of a parallelogram-shaped quartz prism (prism) with an acute angle of 82 °, an incident port of a multi-wave (λ 1, λ 2, λ 3, λ 4, etc.) beam of a front plane thereof is an Antireflection (AR) coated region, the rest thereof is a High Reflection (HR) coated region, and a rear plane thereof is attached with a plurality of narrow-band thin film interference filters (TFF) at respective optical wave output ports thereof. From the schematic diagram, it can be seen that the optical path of the existing thin film interference filter WDM demultiplexer (DeMUX) is spread on a plane, so that the width of the device is much larger than the height of the device in terms of the linearity of the device. A typical four wave device has a width of 3.5mm and a length of 3.92mm, while the height of the device is 1mm, which is small compared to the width and length of the device. If the device is limited in width when in use, for example, the device must be smaller than 2mm, the existing four-wave thin-film interference filter WDM demultiplexer (DeMUX) cannot be used. In addition, the optical path traveled by the fourth wave λ 4 is far larger than the optical path traveled by the first wave λ 1, and the fourth wave λ 4 must accompany the first three waves of light to complete all the optical paths before reaching its output port. The third wave and the fourth wave are much more difficult to couple than the first wave and the second wave. If the existing thin film interference filter WDM demultiplexer (DeMUX) is made into eight waves, the width of the demultiplexer reaches 7mm, the optical path of the seventh and eighth waves is longer, and the general collimator has a difficult collimation distance.
Disclosure of Invention
The purpose of the invention is as follows: in order to overcome the defects that the linearity occupied by the device in the transverse direction is much larger than that occupied by the device in the longitudinal direction, the 3D space cannot be fully utilized, the optical path of the finally emergent light wave is too long, the collimator cannot reach the long collimation distance, and the like, the invention provides a novel WDM demultiplexer based on a thin film interference filter.
The technical scheme is as follows: a WDM demultiplexer based on film interference filter includes a front-stage demultiplexer and a rear-stage demultiplexer arranged in front of a light beam entrance port of the rear-stage demultiplexer, an upper light beam includes light beams of the rear half of the incident light beam with each wavelength, a lower light beam includes light beams of the front half of the incident light beam with each wavelength, an upper and a lower space exists when the upper and the lower parallel light beams exit, and the rear-stage demultiplexer performs re-splitting on the incident upper and the lower parallel light beams.
Furthermore, the pre-stage demultiplexer comprises a pre-stage prism and a band-pass thin-film interference filter arranged at an output port at the lower part of a rear end plane of the pre-stage prism, wherein the band-pass thin-film interference filter totally transmits the light beams with the first half wavelengths in the input light beams and totally reflects the light beams with the second half wavelengths.
Furthermore, the post-stage demultiplexer comprises a post-stage prism and narrow-band thin-film interference filters which are arranged on the rear end plane of the post-stage prism and correspond to the light beam output ports of all paths.
Furthermore, the front-stage prism and the rear-stage prism are both in a parallelogram structure.
Furthermore, the up-down distance required by the outgoing of the upper and lower two parallel beams is obtained by adjusting the acute angle and the length of the preceding stage prism.
Furthermore, the rear-stage prism is composed of two sub-prisms which have the same structure and are stacked up and down.
Furthermore, a plated antireflection film area is arranged at the light beam incident port of the front end plane of the front stage prism and the rear stage prism, and the rest parts are plated high reflection film areas. Furthermore, the bottom surfaces of the front-stage prism and the rear-stage prism are positioned on the same horizontal plane, and the side surface of the rear-stage prism is parallel to the side surface of the front-stage prism.
Furthermore, an antireflection coating area is coated at the upper output port of the rear end plane of the front stage prism of the front stage demultiplexer, and a high reflection coating area is coated between the upper output port and the lower output port of the front stage prism.
Has the advantages that: compared with the prior art, the invention has the following advantages:
1. the optical path of the longest optical wave in the light beam of the wavelength division multiplexing (DeMUX) of the invention is shorter than the optical path of the corresponding optical wave in the existing demultiplexer, and the linearity in the width direction is smaller than that of the existing demultiplexer;
2. when the WDM demultiplexer (DeMUX) is used for splitting light waves into more than four waves (such as six waves, eight waves or more), the characteristics of short optical path and compact structure can be highlighted;
3. the prime prism and the film interference filter pasted on the prime prism are used as a prime demultiplexer, the prime prism divides light waves with various wavelengths of incident collimated light beams into an upper beam and a lower beam which respectively carry parallel light beams with the wavelengths of the first half and the second half, and the upper and lower space distances of the upper beam and the lower beam can be realized by properly designing the acute angle and the prism length of the prime prism;
4. the demultiplexer of the invention can be more compact than the existing thin film interference filter demultiplexer in the width of the device by utilizing the pre-demultiplexing of the front-stage prism and the lamination of the rear-stage prism;
5. the extensibility of each direction of the three-dimensional space is fully utilized, so that the optical demultiplexer (DeMUX) can be made more compact, and meanwhile, the optical path of a long optical path channel is relatively shortened, so that the device is convenient to couple, and the optical demultiplexer (DeMUX) with a plurality of wavelength channels can be manufactured.
Drawings
FIG. 1 is a schematic diagram of a typical optical path and structure of a prior art narrow-band thin-film interference filter-based four-wave WDM demultiplexer (DeMUX);
FIG. 2 is a schematic diagram of a typical optical path and structure of a prior art narrow-band thin-film interference filter-based eight-wave WDM demultiplexer (DeMUX);
FIG. 3 is a schematic diagram of the structure and geometry of a four-wave WDM demultiplexer based on thin-film interference filters according to the present invention;
FIG. 4 is a detailed engineering drawing of a third prism of the present invention;
FIG. 5 is a schematic optical path diagram of a four-wave WDM demultiplexer based on thin-film interference filters according to the present invention;
FIG. 6 is a top view of a four-wave WDM demultiplexer based on thin-film interference filters in accordance with the present invention;
FIG. 7 is a schematic diagram of the structure of an eight-wave WDM demultiplexer based on thin film interference filters according to the present invention.
Detailed Description
The technical solution of the present invention will be further explained with reference to the accompanying drawings and examples.
Example 1:
fig. 3 is a schematic diagram of the structure and geometric configuration of the four-wave WDM demultiplexer based on the thin-film interference filter according to the present invention, which is composed of three prisms, i.e., a first prism 1, a second prism 2, and a third prism 3, wherein the widths of the first prism 1 and the second prism 2 are half of those of the prisms used in the conventional four-wave WDM demultiplexer of fig. 1, and the lengths and heights are the same as those of fig. 1. The light beam incident ports of the front end planes of the first prism 1, the second prism 2 and the third prism 3 are provided with an antireflection coating area AR, the rest parts are high reflection coating areas HR, the upper output port of the rear end plane of the third prism 3 is provided with an antireflection coating area, the part between the upper output port and the lower output port is a high reflection coating area, and two narrow-band thin-film interference filters TFF are respectively attached to the output ports of the rear end planes of the first prism 1 and the second prism 2. The first prism 1 and the second prism 2 are stacked up and down, specifically, the first prism 1 is arranged below the second prism 2, a narrow-band thin-film interference filter TFF for splitting the first wave lambda 1 and the second wave lambda 2 is adhered on an output port of the first prism 1, a narrow-band thin-film interference filter TFF for splitting the third wave lambda 3 and the fourth wave lambda 4 is adhered on an output port of the second prism 2, the third prism 3 is arranged in front of light beam entrance ports of the first prism 1 and the second prism 2, bottom surfaces of the third prism and the first prism are arranged on the same horizontal plane, a side surface of the third prism 3 is parallel to side surfaces of the first prism 1 and the second prism 2, and the third prism 3 is close to the first prism as much as possible under the permission of a space of geometric configuration1And a second prism 2. The third prism 3 is a parallelogram-shaped prism having acute angles, and if the paper plane is taken as an X-Y plane, the horizontal direction to the right on the paper plane is taken as an X direction, and the vertical direction to the paper plane is taken as a Z direction, the third prism 3 is oriented by 90 ° counterclockwise around the X axis similarly to the prism in fig. 1.
A band-pass thin film interference filter TFF is adhered to an output port at the lower part of the rear end plane of the third prism 3, the band-pass thin film interference filter TFF can totally transmit the light waves of the first half of each wavelength in the input light beam and totally reflect the light waves of the second half of each wavelength, the parallelogram acute angle value and the length L value of the third prism 3 are properly set, the light path of the light beams of the totally reflected light waves of the second half of each wavelength is improved by 1mm in the Z direction, thus the input light beams are split into parallel light beams with the vertical interval of 1mm in the Z direction after passing through the third prism 3, each parallel light beam carries half of the wavelength of the light waves of all the wavelengths carried by the input light beams, the two parallel light beams are respectively incident into the first prism 1 and the second prism 2 which are overlapped, and the light beams with different wavelengths are separated in space by the corresponding narrow-band thin film interference filter TFF adhered to the output ports of the first prism 1.
As one of the design solutions of the prism in example 1, fig. 4 shows a detailed engineering drawing of the third prism 3, the third prism 3 having a width of 1mm and a height of 2mm, the third prism 3 having an acute angle of parallel four sides of 82 ° and made of quartz, and a length L of 2.64mm as a prism material.
Specifically, when four waves (λ 1, λ 2, λ 3, λ 4) enter the collimated light beam horizontally and parallel to the side surfaces of the three prisms, the collimated light beam enters the third prism 3, is refracted, and then meets a band-pass thin-film interference filter at the output port below the third prism. The bandpass thin-film interference filter TFF is designed to allow the first wave λ 1 and the second wave λ 2 to be fully transmitted, while the third wave λ 3 and the fourth wave λ 4 are fully reflected, i.e., the third prism 3 is used to divide the light beams λ 1, λ 2, λ 3, λ 4 into two parallel light beams λ 1, λ 2 and λ 3, λ 4. The light beam emitted from the output port below the third prism 3 contains light waves λ 1 and λ 2, and the height of the incident collimated light beam of four waves (λ 1, λ 2, λ 3, λ 4) in the Z-axis direction is appropriately adjusted so that the height of the light beam containing λ 1 and λ 2 from the bottom surface of the first prism in the Z-axis direction is exactly half the thickness of the first prism, and after entering the first prism, the light beam is split horizontally in the first prism and two independent parallel light beams λ 1 and λ 2 are emitted. After being internally reflected for several times in the third prism 3, the light beam containing the lambda 3 and the lambda 4 rises by 1mm in the Z-axis direction when being emitted from an output port at the upper part of the third prism 3, just leads the height of the light beam from the bottom surface of the second prism in the Z-axis direction to be half of the thickness of the second prism, and after being horizontally emitted into the second prism 2, the light beam is spatially split in the horizontal direction through refraction and reflection in the second prism 2 and is emitted into two independent parallel light beams lambda 3 and lambda 4.
By properly adjusting the acute angle and the length L of the parallelogram of the third prism 3, the light beams including λ 3 and λ 4 can always be made to be 1mm higher in the Z-axis direction than the light beams including λ 1 and λ 2 emitted from the third prism 3 when emitted from the third prism 3, so that each light beam can be respectively incident into the first prism 1 and the second prism 2 according to the designed optical path to be split again according to the wavelength.
The optical paths λ 3 and λ 4 in the four-wave WDM demultiplexer (DeMUX) based on the thin-film interference filter of the present embodiment are shorter than the optical paths λ 3 and λ 4 in the four-wave WDM demultiplexer (DeMUX) of the conventional thin-film interference filter in fig. 1. And the linearity in the Y direction is only half that of the four-wave WDM demultiplexer (DeMUX) of the thin film interference filter of fig. 1.
Example 2:
the embodiment combines the first prism 1 and the second prism 2 into a prism with a thickness of 2mm, and the corresponding required narrow-band thin-film interference filter TFF is suitably attached to the output port, and the prism with a thickness of 2mm can perform the same function as the first prism 1 and the second prism 2, but the assembly is simpler.
If the first prism 1 and the second prism 2 are two-wave, the demultiplexer of the present invention is a four-wave demultiplexer, and if the first prism 1 and the second prism 2 are four-wave, the demultiplexer of the present invention may be an eight-wave demultiplexer. As can be seen from fig. 7, the four-wave multiplexer WDM demultiplexer (DeMUX) based on thin film interference filter of the present invention can be easily extended to eight waves, and is much more compact than the existing demultiplexer (DeMUX), and the optical path lengths of λ 5, λ 6, λ 7 and λ 8 are also short. In a similar manner, the demultiplexer of the present invention can be made into a more wave demultiplexer.
The third prism 3 and the band-pass thin-film interference filter attached to it of the present invention are used as a pre-demultiplexer, which divides the light wave with various wavelengths of the incident beam into an upper light wave and a lower light wave, each of which carries the first half and the second half of the wavelength, and the space distance between the upper light wave and the lower light wave can be realized by properly designing the acute angle of the third prism and the length of the third prism. The use of pre-demultiplexing of the third prism 3, the stack of the first prism 1 and the second prism 2, allows the demultiplexer of the present invention to be more compact in device width than existing thin film interference filter demultiplexers. The pre-demultiplexing of the third prism 3 is utilized to divide the light wave with various wavelengths of the incident light beam into an upper light wave and a lower light wave which respectively carry the light wave with the first half and the light wave with the second half of the wavelength, so that when the light wave with the second half of the wavelength completes the final spatial separation of the light waves with various wavelengths, compared with the prior thin film interference filter demultiplexer, the optical path taken by the corresponding light wave is shorter, and the coupling of the light beams of the device is convenient.
Claims (9)
1. A WDM demultiplexer based on thin film interference filters characterized by: the optical fiber multi-wavelength demultiplexing device comprises a front-stage demultiplexer and a rear-stage demultiplexer which are arranged in front of a light beam incident port of the rear-stage demultiplexer, wherein the front-stage demultiplexer divides an incident light beam into an upper beam and a lower beam of parallel light beams, the upper beam of light beam comprises a light beam with each wavelength of the rear half of the incident light beam, the lower beam of light beam comprises a light beam with each wavelength of the front half of the incident light beam, an upper space and a lower space exist when the upper beam of parallel light beam and the lower beam of parallel light beam are emergent, and the rear-stage demultiplexer performs re.
2. A WDM demultiplexer based on a thin film interference filter as claimed in claim 1, wherein: the pre-stage demultiplexer comprises a pre-stage prism and a band-pass thin-film interference filter arranged at an output port at the lower part of a rear end plane of the pre-stage prism, wherein the band-pass thin-film interference filter totally penetrates through the first half of light beams with various wavelengths in the input light beams and the second half of light beams with various wavelengths after total reflection.
3. A WDM demultiplexer based on thin film interference filters according to claim 1 or 2, wherein: the post-stage demultiplexer comprises a post-stage prism and narrow-band thin-film interference filters which are arranged on the rear end plane of the post-stage prism and correspond to the light beam output ports of all paths.
4. A WDM demultiplexer based on a thin film interference filter as claimed in claim 3, wherein: the front-stage prism and the rear-stage prism are both in parallelogram structures.
5. A WDM demultiplexer based on a thin film interference filter as claimed in claim 2, wherein: and the vertical distance required by the outgoing of the upper and lower two parallel beams is obtained by adjusting the acute angle and the length of the preceding stage prism.
6. A WDM demultiplexer based on thin film interference filters as claimed in claim 4, wherein: the rear-stage prism can be composed of two sub-prisms which have the same structure and are stacked up and down.
7. A WDM demultiplexer based on a thin film interference filter as claimed in claim 3, wherein: and the light beam incident ports of the front end planes of the front stage prism and the rear stage prism are provided with antireflection film plating areas, and the rest parts are high reflection film plating areas.
8. A WDM demultiplexer based on a thin film interference filter as claimed in claim 3, wherein: the bottom surfaces of the front-stage prism and the rear-stage prism are positioned on the same horizontal plane, and the side surface of the rear-stage prism is parallel to the side surface of the front-stage prism.
9. A WDM demultiplexer based on a thin film interference filter as claimed in claim 3, wherein: an antireflection coating plating region is arranged at an upper output port of a front-stage prism rear-end plane of the front-stage demultiplexer, and a high reflection coating plating region is arranged between the upper output port and a lower output port of the front-stage demultiplexer.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010280031.2A CN111443431A (en) | 2020-04-10 | 2020-04-10 | WDM demultiplexer based on thin film interference filter |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010280031.2A CN111443431A (en) | 2020-04-10 | 2020-04-10 | WDM demultiplexer based on thin film interference filter |
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| CN111443431A true CN111443431A (en) | 2020-07-24 |
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