TWI287370B - A wave division de-multiplexer - Google Patents

Abstract

The present invention discloses a wave division de-multiplexer (WDDM). It comprises a multiplexer, used for receiving the lights with different wavelengths from the fiber; and a diffraction optical element (DOE), attached on the output port of the multiplexer. The WDDM according to the present invention can effectively filter the lights from the fiber system and improve the efficiency.

Description

1287370 IX. Description of the Invention: [Technical Field] The present invention relates to a wavelength demultiplexer, and more particularly to a wavelength demultiplexer using a diffraction optical element (DOE). [Prior Art] f In the current fast-growing trend in the field of optical fiber communication, the demand for fast and high-capacity communication transmission is increasing. The multi-wavelength/multi-channel (channel) transmission function of the high-density demultiplexer not only increases the transmission capacity, but also eliminates the need to embed new fibers, saving the cost of erection and man-hours. In order to effectively utilize the optical amplification band range provided by the fiber amplifier, it is necessary to reduce the channel spacing. When the channel spacing is as small as 2 nm or less, and the number of channels is increased by multiples of 4, 8, 16, ..., the system is called a wavelength division multiplexing (WDM) system. Please refer to Fig. 1, which is a block diagram of a conventional wavelength multiplexing network. The wavelength multiplex network works by using different wavelengths to correspond to different sensors. A wide-spectrum light wave is introduced from the optical fiber 11·, and different wavelengths are divided into a plurality of optical fibers 11 through the wavelength multiplexing/demultiplexing unit 12 to be sent to different sensing elements 13; and then the light waves returned by the sensing element 13 are Coupled together by fiber coupler 14, output via fiber 11 to enter the wavelength multiplexer/demultiplexer 12. The different wavelengths are then separated and the intensity of the light is detected by the array of detectors. Current issue

5 FE007-P432-TW 1287370 This wavelength multiplexer/demultiplexer 12 mainly adopts three modes: thin film filter (TTF), array waveguide grating (AWG) and fiber grating ( Fiber bragg grating, FBG) The principle of 〇 film filter 是 is the way of coating film, by the principle of vapor deposition, the desired film layer is layered on a thin glass substrate, when the light After different kinds of filters, different wavelengths are filtered out to achieve the effect of splitting. Since the film filter is produced by optical glass substrate and high-low refractive index material (Si〇2 and Guan) by means of phase deposition, the total thickness of the refractive material continuously pressed onto the soil plate on the soil plate will be more The thicker, the more than one hundred layers, the adsorption force of the material attached to the substrate may not be enough to support the entire structure, which easily causes the peeling of the refractive material, the limitation of the shape, and also the development of a narrower distance. An obstacle. The principle of grating is that the physical properties of the waveguide are different, and the technology can divide more channels. The impact of not good money can be completed before a large number of commercializations. ^Technical barrier: It is also the most difficult problem of the current arrayed waveguide grating. Interfering with the periodic fiber with different refractive index generated by the target position becomes a Bragg grating. Using optical diffraction (four)...#?, b agg) characteristics of the light source of different wavelengths

FE007-P432-TW 1287370 is out, so the optical signal can be separated narrower than the thin film filter. However, in order to avoid the fiber grating used for diffraction, the output is affected by temperature. The splitting power of the wavelength multiplex/demultiplexer and the loss of the fiber itself in different bands limit the number of sensing elements. Especially in the WDDM system, it is necessary to separately analyze the signals of different optical wavelengths in the optical fiber. Traditionally, it has been conventional to increase the transmission speed of the optical fiber 11 in order to increase the transmission efficiency of the optical fiber. However, only increasing the speed of the fiber 11 will always reach the limit. In summary, the low spectral efficiency of the conventional wavelength demultiplexer is the biggest drawback. Therefore, in order to solve this problem, it is necessary to provide a wavelength demultiplexer having a selective spectroscopic function from overcoming the disadvantages of the prior art. SUMMARY OF THE INVENTION The object of the present invention is to provide a wavelength demultiplexer that uses an optical diffraction element at an optical signal input end of the wavelength demultiplexer to effectively resolve signals of different optical wavelengths in the optical fiber. Come out to improve the splitting efficiency of the wavelength multiplexer. To achieve the above object, the present invention provides a wavelength demultiplexer comprising a multiplexer and a light diffractive element. The multiplexer is configured to receive light waves having a wide spectral range in the optical fiber, and the optical diffractive component is disposed at an optical signal output end of the multiplexer for separately analyzing signals of different optical wavelengths. The light diffractive element further comprises a plurality of light diffractive element crystals having a geometric shape having a thickness that varies in a complex order.

FE007-P432-TW 1287370 is a feature of one of the long-range multi-guards, which is an integer multiple of the order of the light diffraction. Cheng production, can be used to make = / long solution multi-guard system to micro-electromechanical system, to achieve the resolution of multi-fiber fiber different wavelengths of light separately resolved significantly = this ^ ^ fans and other purposes, features, and advantages DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As a preferred embodiment, and in conjunction with the accompanying drawings [Embodiment] Although the present invention can be used to rent a beta and the following (d) j is a different form of embodiment, but the drawings please understand this article DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(B) </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; </ RTI> <RTIgt; schematic diagram. The figure shows the structure of the wavelength demultiplexer 12A. The wavelength demultiplexer 12 includes a multiplexer 12i and a light diffractive element 123. The multiplexer 121 is for receiving light waves having a wide spectral range in the optical fiber, and is used as the body of the wavelength demultiplexer 120. The multiplexer 121 is positioned as the wavelength multiplexer/demultiplexer 12 in the basic functional diagram of Fig. 1. The diffraction optics element (DOE) 123 is configured in s

FE007-P432-TW 1287370: Two-terminal end, used to resolve signal pulses of different wavelengths of light. The substrate of the light diffraction element 123 is a material of a glass substrate, a thick film of indium tin oxide and a transparent photoresist, and the 123 is made by a microelectromechanical or semiconductor process: small to understand the wavelength of the present invention The principle and characteristics of the solution are shown in Fig. 3, which shows the difference in function and appearance between the light diffractive element 123 and the light refraction S piece used in the present invention. Light diffraction elements Micro-optical - an important application. For the active optics element (R0E) * the 'diffraction phenomenon only occurs on the aperture, that is, the diffraction phenomenon does not have the function of modulating the penetrating optical element. The optical quality of f兀: is diffracted. The limitation (Dlffr she on Llmlt), this limitation on diffraction X is particularly noticeable in tiny lens arrays (micro_lensarray). Next, please refer to the above description and Fig. 4b for explaining the principle of splitting of the optical diffraction element 123 of Fig. 3. In Fig. 4a, when the shape of a ^ front is not a plane wave, it can be mathematically performed by Fourier transform, and this - the wavefront can be composed of many plane waves of different intensities. In Fig. 4b, when the flat light is incident on the light diffractive element 123, the wavefront changes. When controlling the surface shape of the light diffractive element 123 (immediately, the traveling direction of different incident waves can be controlled. Since the refractive index n of the substrate medium and the thickness will affect the wavelength, the design can affect the wavelength. The direction of advancement 'step-by-step wavelengths from different directions to solve what we need

The FE007-P432-TW 1287370 signal, which is not intended to be resolved, will be directly penetrated by the light diffractive element 123. Please refer to Fig. 5, which is a side view showing the detailed structure of the light diffraction element. The light diffractive element 123 further includes a plurality of light diffraction unit cells 124, wherein the thickness of the plurality of light diffraction unit cells 124 is in a complex order periodically varying geometry. The basic principle of the light diffractive element 123 is phase modulation, using scalar diffraction theory or vector diffraction theory, which is calculated to obtain a change in surface profile. After the invention of holography, the concept and principle of diffractive optics were further applied to micro-optical components; such as beam splitters and Lenslets. The basic design flow of the light diffractive element 123 is to first calculate the interference pattern of a particular wavefront, which is a computer-generated hologram (CGH). Then, the digital plotter output calculates the simulated interference pattern, and finally the miniature image is the final film. The phase of the light field on the incident surface is modulated by the change of the surface profile, and the phase of the exiting light field is controlled to obtain a distribution of the spatial energy of the predetermined outgoing light. The design rule of the light diffractive element 123 is roughly divided into four structures: the first is an optical path method; the second is a scalar diffraction theory; the third is Rigorous coupled wave theory; the fourth is effective medium theory. The light diffractive element 123 of the present invention is preferably designed by a scalar wave diffraction method. The 9-quantity wave diffraction method describes the diffraction phenomenon of light based on the fluctuation of light. Also known as fourier optics. The wave of light says that the wavefront

Ίο FE007-P432-TW 1287370 The mother-point material is considered to be a secondary (sec〇ndary) ball source, ie the wave packets of all new wave sources will form a new wavefront. The light/piece 123 bites the forward direction of the light passing through the light diffraction element 123 in accordance with the wavelength of the human/external light and the refraction of the substrate. The diffraction efficiency is related to the plurality of light diffraction unit cells 124 on the diffractive diffraction element 123. It should be noted that the number of the plurality of light diffraction unit cells 124 has an integer multiple of 2 and has a periodic variation of the fourth-order thickness; the length of the plurality of light diffraction unit cells 124 is 16 μm. For a cycle. The dielectric thickness of the plurality of light diffraction unit lattices 二 24 determines the diffraction direction of the incident light wavefront. The plurality of light diffraction unit lattices 124 are used to disperse light of a plurality of beams in different directions and angles to achieve uniform energy distribution. The surface of the plurality of light diffraction unit cells 124 has a thickness of no more than 1 Oum. The diffraction angle of the plurality of light diffraction unit cells 124 is no more than 90 degrees. According to the wavelength demultiplexer 120 disclosed in the present invention, the design steps of the light diffraction element 123 (DOE) are as follows: (1) Find the thickness of the surface medium that does not affect the shape of the wavefront, and if the wavelength of the light is λΐ, Then, when the surface medium thickness =, the wavefront shape of the light passing through the material does not change. For example, the following three communication wavelengths λ ΐ, λ 2 and λ 3 are used, which are 850 nm, 1310 nm, and 1550 nm, respectively. The disassembly rate of the medium is η=ι·5, and the surface dielectric thickness Dn(x) which does not affect the traveling direction of the wavefront is calculated.

II FE007-P432-TW 1287370 is 〇) = 7 meaning]-', so the respective thicknesses of the communication wavelengths of 850nm, 1310nm and 1550nm are not affected, respectively Di(x) = L7um, D2(x) = 2.62um and D3 (x) = 3.1um. (2) Refer to Figure 6a to calculate the minimum common multiple of the surface dielectric thickness of the wavefront that does not affect λΐ and λ3, ie D3(x), DJx) m31=5.27um. Among them, after design calculation, the wavelength of λ2 is deflected by m31 as the layer thickness, while the wavelength of λΐ and λ3 is not deflected, and the surface dielectric thickness of DOE is DKx). (3) Refer to Figure 6b to calculate the thickness of the medium that does not affect the wavefront of λ2 and λ3, that is, the least common multiple of D2(x) and D3(x) m32=8.12um. Wherein, the thickness of the surface medium is Di(x). (4) Please refer to Figure 6c. If you combine steps (2) and (3), you can evenly resolve the three light rays λΐ, λ2 and λ3. Among them, the surface medium thickness is Di(x) + D2(x). Please refer to Fig. 7, which shows the design flow of the light diffractive element 123. First, the diffraction efficiency and the diffraction angle of the emitted light are calculated, and the structure of the light diffraction unit cell 124, the thickness and the period of the surface medium are determined by a program analysis. The preferred embodiment of the light diffraction unit cell 124 is a stepped periodic structure having a surface dielectric thickness of about 5 um or less and an 8th order period. Again with Figure 5 to illustrate the DOE process. There are three types of DOE manufacturing methods: hologram recording, mask lithography (yellow lithography), and direct recording. The preferred embodiment of the invention employs, but is not limited to, a reticle lithography (yellow lithography) process. On a transparent substrate, such as quartz, glass

Ία FE007-P432-TW 1287370 Glass substrate, indium tin oxide thick film (IT0) or transparent photoresist, produced by the traditional photochrome (yellow lithography) process. In order to produce a plurality of light diffraction single s lattices 124 of different depths, multiple yellow lithography and side processes can be employed. Or, using gray scale light I, since the photoresist has different exposure depths in different colors of the gray scale mask, different light diffraction unit cells 124 can be achieved. The photoresist is used but not limited to the eight 2 positive photoresist series and the SU: 8 negative photoresist series. Other thick film photoresists can also be implemented. On the other hand, due to the rapid development of the electromechanical process (MEMS) technology, the need for miniaturization of components, the plurality of light diffraction unit lattices 124 of the light diffraction element 123 can also use U-like micro-electromechanical The system is based on the use of the upper semiconductor process to make a similar complex number, the diffraction mode of the unit 124 of the cell, and then a layer of transparent polyoxyalkylene polymer PDMS or similar The material, after being baked, is demolded to obtain a light diffraction element 123 having a surface medium thickness of about 5 um. The plurality of light diffraction unit lattices 124 of the light diffraction element 123 have an integer multiple of 2 The preferred embodiment is a fourth order. • In the red, in order to break through the bottleneck on the fiber transmission wheel and solve the shortcomings of the conventional multiplexer/demultiplexer, the present invention discloses a wavelength demultiplexer 120. It is used to increase the speed of fiber transmission, and increase the number of emitted light, the number of readings and the number of reading lights, thereby increasing the flow rate of reading data to a multiple of the reading of the multiplex wavelength multiplexer. The DOE is used according to the present invention. The wavelength resolution multiplexer 120 of the piece can effectively Different fiber length of the light wave signals are parsed, to improve the spectral efficiency of the wavelength multiplexer.

FE007-P432-TW -!28737〇: The invention has been disclosed in the foregoing preferred embodiments, but it is not the invention, and anyone skilled in the art can Can make a variety of changes and modifications. If the above = off can be used to make corrections and changes of various types, the division will destroy the spirit. Therefore, the invention of the present invention is subject to the definition of the patent attached to the patent. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features, and advantages of the present invention will become more apparent. 1 is a block diagram of a conventional wavelength multiplexing network; FIG. 2 is a wavelength demultiplexer in accordance with the present invention; and FIG. 3 is shown in a functional and external form of the diffractive optical element 123 and the refractive optical element. The difference is shown in Fig. 4a as a schematic diagram of a plurality of different directions and intensity obtained by Fourier transform of plane light; and Fig. 4b illustrates the principle of splitting of the light diffraction element 123 of Fig. 3; Fig. 5 is not Side view of the detailed structure of the light diffraction element; f 6a shows the diffracted light path when the medium thickness is D2(x); 6b shows the diffracted light path when the medium thickness is Dl(x); Figure 6C shows It is a diffracted light path when the medium thickness is Dl(x)+D2(x); and Fig. 7 shows the design flow of the light diffractive element.

1# FE007-P432-TW 1287370 [Major component symbol description] 100 conventional wavelength multiplex network 110 fiber 120 wavelength demultiplexer 121 wavelength multiplexer 122 wavelength solution multiplexer 123 light diffraction element f 124 light winding Shot element lattice

15 FE007-P432-TW

Claims (1)

1287370 X. Patent Application Range: 1. A wavelength demultiplexer comprising: a multiplexer for receiving a wide range of light waves in a spectral range of an optical fiber; and a light diffractive element disposed in the multiplex The optical signal output end of the device is configured to separately parse signals of different optical wavelengths; wherein the optical diffractive element further comprises a plurality of optical diffractive element crystal lattices having a geometric shape having a thickness of a plurality of stages. 2. The wavelength demultiplexer of claim 1, wherein the substrate of the light diffraction element is selected from the group consisting of a glass substrate, a thick film of indium tin oxide, and a transparent photoresist. 3. The wavelength demultiplexer of claim 1, wherein the light diffraction element is fabricated by a microelectromechanical process. 4. The wavelength demultiplexer of claim 1, wherein the number of lattices of the light diffraction unit has an integer multiple of two. 5. The wavelength demultiplexer of claim 4, wherein the light diffraction unit lattice is a periodic variation of a fourth order thickness. 6. The wavelength demultiplexer of claim 4, wherein the length of the light diffraction unit lattice is 16 um. The invention relates to a wavelength demultiplexer according to claim 1, wherein the dielectric thickness and refractive index of the light diffraction unit lattice determine the diffraction direction of the incident light wavefront. 8. The wavelength demultiplexer according to item 2 of the patent application, wherein the thickness of the plurality of light diffraction unit crystal lattices is not more than l〇um. 9. The wavelength demultiplexer according to item 2 of the patent application scope. , wherein the diffraction angle of the plurality of light diffraction unit lattices is no more than 90 degrees. 17 FE007-P432-TW