CN108398743B - AWG router for realizing spectrum uniformity by cascading filter and input channel - Google Patents
AWG router for realizing spectrum uniformity by cascading filter and input channel Download PDFInfo
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- G—PHYSICS
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- G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G02B6/00—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings
- G02B6/10—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type
- G02B6/12—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind
- G02B6/12007—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer
- G02B6/12009—Light guides; Structural details of arrangements comprising light guides and other optical elements, e.g. couplings of the optical waveguide type of the integrated circuit kind forming wavelength selective elements, e.g. multiplexer, demultiplexer comprising arrayed waveguide grating [AWG] devices, i.e. with a phased array of waveguides
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- 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
- G02B6/29304—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 diffraction, e.g. grating
- G02B6/29316—Light guides comprising a diffractive element, e.g. grating in or on the light guide such that diffracted light is confined in the light guide
- G02B6/29317—Light guides of the optical fibre type
- G02B6/29319—With a cascade of diffractive elements or of diffraction operations
- G02B6/2932—With a cascade of diffractive elements or of diffraction operations comprising a directional router, e.g. directional coupler, circulator
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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
- G02B6/29379—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 characterised by the function or use of the complete device
- G02B6/2938—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 characterised by the function or use of the complete device for multiplexing or demultiplexing, i.e. combining or separating wavelengths, e.g. 1xN, NxM
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
- H04Q11/0001—Selecting arrangements for multiplex systems using optical switching
- H04Q11/0005—Switch and router aspects
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q11/00—Selecting arrangements for multiplex systems
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Abstract
The invention discloses an AWG router for realizing spectrum uniformity by cascading a filter and an input channel. The free spectral range is larger than the channel wavelength interval of 2 XN times of the array waveguide grating, the array waveguide grating is provided with 2N-1 input/output channels, and the central input port of the array waveguide grating is connected with the filtering input waveguide through the AWG input waveguide; the N-th input port and the n+n-th input port form a group of input ports in other input ports, and are respectively connected to the output end of the same filter through respective AWG input waveguides, and the N-1 filter input ends are respectively connected with the other N-1 filter input waveguides. The invention realizes the uniform insertion loss of the output spectrum, can effectively reduce the insertion loss difference of all output channels, effectively reduces the serious output wavelength frequency deviation caused by the incapability of realizing the free spectrum range requirement and the diffraction order as integers at the same time, and has the advantages of simple manufacture, low cost and the like.
Description
Technical Field
The invention relates to an Array Waveguide Grating (AWG) optical wavelength router, in particular to an AWG router with a filter and an input channel in cascade connection to realize uniform frequency spectrum.
Background
As the minimum feature size of semiconductor processes continues to decrease according to moore's law, chip integration becomes higher and higher, and the data exchange speed between transistors cannot keep pace with the data processing speed itself, and metal conduction-based electrical interconnection technologies are facing insurmountable "electronic bottlenecks". Compared with the electric interconnection, the optical interconnection (Optical Interconnect) takes photons as an information carrier, has the advantages of ultra-high bandwidth, ultra-fast transmission rate, electromagnetic interference resistance, low energy consumption and the like, and can bring about a new information industry revolution.
The silicon-based optical interconnection technology has the advantages of low power consumption, compatibility with a semiconductor CMOS process, integration, low cost and the like, and is an ideal platform for realizing the optical interconnection between chips and on-chip. The optical wavelength router can realize the intelligent distribution of the uplink/downlink wavelength of the optical node, the route switching of the high-speed non-blocking optical domain, the transparent transmission is ensured, and the optical wavelength router is one of core devices of an optical interconnection network system.
The optical wavelength router may be implemented by a Ring resonator (Ring resonator), an Etched Diffraction Grating (EDG), or the like. However, when more wavelength channels and fabrication requirements are considered, arrayed Waveguide Gratings (AWGs) are one of the best choices for optical wavelength routers. The AWG has the advantages of compact structure, easy integration, excellent performance, high reliability and the like. Optical wavelength routers composed of n×n type Arrayed Waveguide Gratings (AWGs) are becoming a research hotspot.
For a common arrayed waveguide grating optical wavelength router, the central wavelength of the router is represented by a grating equation n c ΔL＝mλ c (formula 1) determination, wherein n c Is the effective refractive index of the array waveguide, delta L is the length difference of adjacent array waveguides in the array waveguide area, m is the diffraction order, lambda c Is the center wavelength. Its free spectral range is expressed asWherein N is c Is the group index of refraction of the arrayed waveguide. In an nxn optical wavelength routing application, the FSR of the AWG is required to be exactly N times the channel spacing, while the diffraction order m must be an integer. Generally, both equations cannot be satisfied at the same time. The array waveguide length difference can be obtained only by the formula (2), and the diffraction order m obtained by substituting the formula (1) is rounded nearby. The FSR, which is back-pushed again according to the integer m, deviates from the actual requirement, causing a more serious frequency deviation phenomenon. Also in this case, the output spectrum of the remaining input channels except the center channel needs to be used for the spectrum with the diffraction order of m-1 or m+1, and since the energy is mainly distributed in the m diffraction order, the energy distribution of different diffraction orders has a relatively large difference, so that the optical wavelength router faces the difficulty of implementing the uneven insertion loss of the channel in a free spectral range. In particular, for one input channel, the insertion loss difference of the spectrums of all the output channels is at least 3dB, and for the corresponding output spectrums of all the input channels, the loss difference is at least 6dB.
The method for reducing the transmission loss difference of the array waveguide grating optical wavelength router reported at home and abroad mainly comprises a wave front mode matching method using a mode converter at the joint of an array waveguide and an output flat waveguide area and a method for adding an auxiliary waveguide between the array waveguides. Sakamaki Y, kamei S, hashimoto T, et al, loss Uniformity Improvement of Arrayed-Waveguide Grating With Mode-Field Converters Designed by Wavefront Matching Method [ J ]. Journal of Lightwave Technology,2009,27 (24): 5710-5715, mentions a wavefront mode matching method that uses a mode converter at the junction of the array waveguide and the output slab waveguide region. The mode converter converts the fundamental mode in the array waveguide into a far field distribution having a plateau effect at the interface between the output slab region and the output waveguide. This approach reduces the loss difference from 2.4dB to 0.7dB for the loss of the output spectrum corresponding to one input channel. The article of Sheng Z, dai D, he S.Imtive Channel Uniformity of an Si-Nanowire AWG Demultiplexer by Using Dual-Tapered Auxiliary Waveguides [ J ]. Journal of Lightwave Technology,2007,25 (10): 3001-3007 mentions that auxiliary waveguides are added between the array waveguides at the connection of the array waveguides and the output slab waveguide to realize the spectrum homogenization of the array waveguide grating wavelength demultiplexer. The design allows the difference of the spectrum loss of 12 output channels to be less than 0.5dB.
Both of these approaches have successfully reduced the output spectral loss difference of arrayed waveguide grating optical wavelength routers. But only for the output spectrum corresponding to one input channel, there is still a 3dB difference in loss for all input channels due to the use of other diffraction orders.
Disclosure of Invention
Aiming at the defects of the background technology, the invention aims to provide an AWG router which is formed by cascading a filter and an input channel and realizes uniform frequency spectrum, and the filter and the input channel are additionally connected on the basis of an Array Waveguide Grating (AWG) so as to solve the problem of larger frequency spectrum insertion loss difference of the traditional array waveguide grating optical wavelength router and realize uniform frequency spectrum loss.
An optical wavelength router is one of core devices in optical interconnection, optical communication, and the like, and is required to have a wavelength circulation routing function of all output channels. Optical wavelength routing can be achieved by using an n×n arrayed waveguide grating with N input channels and N output channels, where the free spectral range of the arrayed waveguide grating is equal to the product of the number of output channels and the output channel spacing, and the diffraction order of the grating is m. In this case, however, the output spectra corresponding to the other input channels, except the center channel, all require the use of either m-1 or m+1 diffraction orders. This results in an insertion loss difference of at least 3dB for all output channels corresponding to the central channel of the nxn arrayed waveguide grating router, and a spectral difference of at least 6dB for all input channels.
In order to reduce the loss difference, realize the uniform loss of all channels, unlike the design of the traditional array waveguide grating optical wavelength router, the invention designs an array waveguide grating with a free frequency spectrum range larger than N channel widths, and according to the corresponding relation between input and output, adopts a method of adding a cascade Mach-Zehnder interferometer (MZI) or other filters in front of two specific input waveguides to divide input light into two beams to be respectively input into corresponding input channels, and only utilizes m diffraction orders to realize the purpose that the output frequency spectrums corresponding to other input channels except the central input channel can also realize the uniform spectrum loss. The invention is applicable to various waveguide materials and waveguide structures based on silicon dioxide, silicon nitride, silicon oxynitride, indium phosphide, and the like.
The aim of the invention is realized by the following technical scheme:
the invention comprises N filtering input waveguides, N-1 filters, 2N-1 AWG input waveguides, an array waveguide grating and N output waveguides; the free spectral range is larger than the 2 XN times channel wavelength interval in the array waveguide grating, the array waveguide grating is provided with 2N-1 input/output channels, and the central input port (namely the N input port) of the array waveguide grating is connected with the 1 st filtering input waveguide through an AWG input waveguide; for other input ports except the central input port in the array waveguide grating, the nth input port and the n+nth input port form a group of input ports, the N input ports and the n+nth input port are respectively connected to the output end of the same filter through respective AWG input waveguides, the total N-1 group of input ports are connected to N-1 filters, and the input ends of the N-1 filters are respectively connected with the other N-1 filtering input waveguides.
The filter is a 1×2 filter, and the input light is subjected to spectral processing.
N light in the intermediate wavelength in the diffraction order wavelength range is input into N filtering input waveguides and then enters the array waveguide grating, light input from the other N-1 filtering input waveguides except the 1 st filtering input waveguide is split into two light beams with different wavelengths through respective filters, then the two light beams enter two input channels of the array waveguide grating respectively, and then the light beams are output from the output waveguide after being routed through the array waveguide grating wavelength, namely the light beams are sequentially transmitted to N output waveguides through an input slab waveguide area, an array waveguide area and an output slab waveguide area of the array waveguide grating.
Therefore, the invention only inputs N wavelengths in the middle of the diffraction order wavelength range into the array waveguide grating, so that the purpose of uniform spectrum loss is realized for the output spectrums corresponding to all input channels of the array waveguide grating, namely, the purpose of uniform spectrum loss is realized for the output spectrums corresponding to other input channels except for the central input channel of all input channels of the array waveguide grating.
The Array Waveguide Grating (AWG) mainly comprises an input slab waveguide area, an array waveguide area and an output slab waveguide area which are sequentially arranged from input to output, wherein the array waveguide area is positioned between the input slab waveguide area and the output slab waveguide area.
In the invention, the array waveguide grating corresponding to N input/output channels has N channel wavelength intervals smaller than the whole free spectrum range of the array waveguide grating light wavelength, namely FSR > nΔλ, wherein FSR is the free spectrum range of the array waveguide grating light wavelength router, and Δλ is the channel spacing of the array waveguide grating light wavelength router.
According to the invention, a 1 multiplied by 2 filter and two AWG input waveguides 3 thereof are specially adopted as basic unit cascading at a non-central input port of the array waveguide grating, so that the array waveguide grating with a free spectral range larger than N times of channel wavelength interval realizes the N multiplied by N wavelength routing effect.
The input ports except the central input port of the array waveguide grating are input by adopting a 1 multiplied by 2 filter and cascade connection with two AWG input waveguides, so that when the output frequency spectrum corresponding to a part of light with a certain wavelength does not meet the AWG wavelength routing condition after the original input light is input to the corresponding channel of the array waveguide grating, the part of light with the certain wavelength in the original input light is introduced into the other input channel except the corresponding channel of the array waveguide grating according to the wavelength routing relation between the wavelength inside the array waveguide grating and the input and output channel, and further, all the output frequency spectrums of the original input light input to the array waveguide grating meet the AWG wavelength routing condition, so that the function of wavelength routing is realized.
The filter adopts a cascade Mach-Zehnder interferometer structure, and other filters capable of achieving the same light splitting effect can be adopted.
In the invention, an array waveguide grating with a free spectral range larger than 2N channel widths is adopted, the diffraction order is m, the array waveguide grating is provided with 2N-1 input channels, the Nth input channel is a central channel, the N output channels, and N-1 cascade Mach-Zehnder interferometers or other 1X 2 filters are added in front of the input waveguide.
Table 1 shows the two input waveguides and the corresponding wavelength distribution ranges that are connected when the beam is split into two by the filter. The first column is the input channel connected with one branch of the filter, the third column is the input channel connected with the other branch of the filter, and the second column and the fourth column are the allocated wavelengths corresponding to the two branches of the filter respectively. A filter such as the n+1th input waveguide connection splits the input light into λ 2 ～λ N And lambda 1, lambda 2 ～λ N Is introduced into the (n+1) th input waveguide, lambda 1 Is introduced into the 1 st input waveguide. Because the free spectral range of the array waveguide grating is larger than 2N channel intervals, the output frequency spectrums of all input channels are in m diffraction orders through the processing, the problem of deviation of center wavelength of the frequency spectrums can be avoided, and the loss difference of each output channel is smaller under the same diffraction order, so that the effect of uniform frequency spectrum loss can be realized.
TABLE 1 connection of filters to input channels and wavelength distribution relationship
The invention has the beneficial effects that:
1. the array waveguide grating router which adopts a cascade structure of a 1 multiplied by 2 filter and two specific input waveguides to realize uniform insertion loss of an output frequency spectrum can effectively reduce the insertion loss difference of all output channels except for the central input channel.
2. The invention discloses an array waveguide grating router which adopts a filter and two specific input waveguide cascade structures to realize uniform loss of the output spectrum insertion loss, and can effectively reduce serious output wavelength frequency deviation caused by incapability of realizing the free spectrum range requirement and the diffraction order as an integer.
3. The array waveguide grating router which adopts a filter and two specific input waveguide cascade structures to realize uniform output spectrum insertion loss except for the central input channel can be applied to array waveguide grating optical wavelength routers with different materials and different waveguide structures, and has the advantages of simple manufacture, low cost and the like.
Drawings
Fig. 1 is a schematic wavelength routing diagram of an arrayed waveguide grating optical wavelength router.
Fig. 2 is a schematic structural diagram of a conventional arrayed waveguide grating optical wavelength router.
Fig. 3 is a schematic wavelength routing diagram of an arrayed waveguide grating optical wavelength router of the present invention.
Fig. 4 is a schematic diagram of the structure of a cascaded mach-zehnder interferometer filter.
Fig. 5 is a schematic structural diagram of an arrayed waveguide grating optical wavelength router of the present invention.
Fig. 6 is a spectrum diagram of the cascaded mach-zehnder interferometer filter after filtering.
Fig. 7 is an output spectrum diagram of a 4×4 conventional arrayed waveguide grating optical wavelength router.
Fig. 8 is an output spectrum plot of input channel 3 and input channel 7 of an arrayed waveguide grating optical wavelength router employing the present invention 4*4.
Fig. 9 is an output spectrum plot of the input channel 4 of an arrayed waveguide grating optical wavelength router employing the present invention 4*4.
Fig. 10 is an output spectrum plot of input channel 5 and input channel 2 of an arrayed waveguide grating optical wavelength router employing the present invention 4*4.
Fig. 11 is an output spectrum plot of input channel 6 and input channel 1 of an arrayed waveguide grating optical wavelength router employing 4*4 of the present invention.
In the figure: a filter input waveguide 01, a filter 02, an AWG input waveguide 03, an arrayed waveguide grating 04 and N output waveguides 05.
Detailed Description
The invention is further described below with reference to the drawings and examples.
Shown in fig. 1 is a wavelength routing schematic of a 4 x 4 arrayed waveguide grating optical wavelength router. The central input channel is input channel 2.
The wavelength routing function of the arrayed waveguide grating optical wavelength router is as follows: when the wavelength lambda is 1 ,λ 2 ,λ 3 ,λ 4 When light is input from the input channel 1, the wavelength of the output light from the output channel 1 to the output channel 4 is lambda 'in turn' 4 ,λ 1 ,λ 2 ,λ 3 The method comprises the steps of carrying out a first treatment on the surface of the When the wavelength lambda is 1 ,λ 2 ,λ 3 ,λ 4 When light is input from the input channel 2, the wavelength of the output light from the output channel 1 to the output channel 4 is lambda in turn 1 ,λ 2 ,λ 3 ,λ 4 The method comprises the steps of carrying out a first treatment on the surface of the When the wavelength lambda is 1 ,λ 2 ,λ 3 ,λ 4 When light is input from the input channel 3, the wavelength of the output light from the output channel 1 to the output channel 4 is lambda in turn 2 ,λ 3 ,λ 4 ,λ” 1 The method comprises the steps of carrying out a first treatment on the surface of the When the wavelength lambda is 1 ,λ 2 ,λ 3 ,λ 4 When light of (2) is input from the input channel 4, the light is outputThe wavelength of the output light from channel 1 to output channel 4 is in turn lambda 3 ,λ 4 ,λ” 1 ,λ” 2 . Lambda' represents the output wavelength when the diffraction order is m-1, and lambda "represents the output wavelength when the diffraction order is m+1.
When the arrayed waveguide grating is used for an optical wavelength routing function, since the adjacent three free spectral ranges are different, the output wavelengths of the edge channels can have larger frequency deviation due to the fact that the output wavelengths of the other channels are not in the same diffraction order. For example lambda' 2 ≠λ 2 This problem is particularly acute for arrayed waveguide grating optical wavelength routers of silicon nanowires, due to the large material dispersion of silicon. Moreover, the difference in loss of the respective output channels is large due to the difference in energy caused by the difference in diffraction orders.
To implement the wavelength routing function, the free spectral range of the arrayed waveguide grating optical wavelength router is the product of the number of input/output channels and the channel wavelength spacing, expressed as:
FSR＝N×Δλ
wherein N is the number of input/output channels of the arrayed waveguide grating optical wavelength router, and Δλ is the channel wavelength spacing of the arrayed waveguide grating optical wavelength router.
As shown in fig. 2, the conventional arrayed waveguide grating optical wavelength router includes N input waveguides, an input slab waveguide region, an arrayed waveguide region, an output slab waveguide region, and N output waveguides;
the center wavelength of the conventional arrayed waveguide grating optical wavelength router satisfies the following diffraction equation:
n c ΔL＝mλ c
wherein lambda is c And m is the diffraction order.
The free spectral range of a conventional arrayed waveguide grating optical wavelength router can be expressed by the following equation:
wherein N is c Is an array ofGroup refractive index of the waveguide.
In n×n optical wavelength routing applications, the free spectral range of the arrayed waveguide grating is required to be exactly N times the channel spacing, i.e., fsr=n×Δλ is required to satisfy equation (1). After the number N of input/output channels and the channel spacing delta lambda of the conventional arrayed waveguide grating optical wavelength router are determined, the free spectral range FSR of the conventional arrayed waveguide grating optical wavelength router is determined.
Because of the central wavelength lambda of the traditional array waveguide grating optical wavelength router c It has been determined that the length difference deltal between two adjacent waveguides in the array waveguide region of the conventional array waveguide grating optical wavelength router can be obtained by the method (3). Then ΔL is substituted into formula (2), so that the diffraction order m of the conventional arrayed waveguide grating optical wavelength router can be obtained, and since m must be an integer, the free spectral range generally cannot satisfy formula (1), so that the output spectrums of the other input channels except the center channel need to be used for spectrums with diffraction orders of m-1 or m+1, and a serious frequency deviation phenomenon can be caused.
As shown in fig. 3, the AWG router structure of the present invention includes N filter input waveguides 01, N-1 filters 02, 2N-1 AWG input waveguides 03, an arrayed waveguide grating 04, and N output waveguides 05; the free spectral range is larger than the 2N times channel wavelength interval in the array waveguide grating 04, the array waveguide grating 04 is provided with 2N-1 input/output channels, and the central input port (namely the N input port) of the array waveguide grating 04 is connected with the 1 st filtering input waveguide 01 through an AWG input waveguide 03; for other input ports except the central input port in the arrayed waveguide grating, the nth input port and the n+nth input port form a group of input ports, the N input ports and the n+nth input port are respectively connected to the output end of the same filter 02 through respective AWG input waveguides 03, the total N-1 group of input ports are connected to N-1 filters 02, and the input ends of the N-1 filters 02 are respectively connected with the rest N-1 filtering input waveguides 01.
The light with N intermediate wavelengths in the diffraction order wavelength range is input into N filtering input waveguides 01 and then enters an array waveguide grating 02, the light input from the rest N-1 filtering input waveguides 01 except the 1 st filtering input waveguide 01 is split into two light beams with different wavelengths through respective filters, then the two light beams enter two input channels of the array waveguide grating 04 respectively, and then the light beams are output from an output waveguide 05 after being routed through the wavelengths of the array waveguide grating 04.
The arrayed waveguide grating AWG mainly comprises an input slab waveguide area, an arrayed waveguide area and an output slab waveguide area which are sequentially arranged from input to output, wherein the arrayed waveguide area is positioned between the input slab waveguide area and the output slab waveguide area.
The other input ports except the central input port of the array waveguide grating 02 are input by adopting a 1×2 filter and cascading two AWG input waveguides 03, so that when the output frequency spectrum corresponding to a part of wavelength light does not meet the AWG wavelength routing condition after the original input light is input to the corresponding channel of the array waveguide grating 02, the part of wavelength light in the original input light is introduced into the other input channel except the corresponding channel of the array waveguide grating 02 according to the wavelength routing relation between the wavelength inside the array waveguide grating 02 and the input and output channel, and then all the output frequency spectrums of the original input light input to the array waveguide grating 02 meet the array waveguide grating 02 wavelength routing condition, so that the function of wavelength routing is realized.
The filter 02 is a 1×2 filter, and performs spectral processing on input light. In the specific implementation, the filter adopts a cascade Mach-Zehnder interferometer structure, and other filters which can achieve the same light splitting effect can also be adopted.
The working principle of the invention is as follows:
fig. 3 is a schematic wavelength routing diagram of an arrayed waveguide grating optical wavelength router of the present invention. FSR of array waveguide grating optical wavelength router with channel interval delta lambda>8 x Δλ. The input port 4 serves as a central input channel. Lambda (lambda) 2 Is the center wavelength. According to the illustration, the input ports and output ports are numbered first. The input ports 3 to 6 correspond to the output ports 3 to 6. According to the principle of the array waveguide grating, the lambda is obtained 1 ,λ 2 ,λ 3 ,λ 4 The correspondence between the input ports and the output ports is the same for the four wavelengths.
TABLE 2 correspondence between input and output ports
As shown in Table 2, for input port 4, there is λ 1 ,λ 2 ,λ 3 ,λ 4 Light of four wavelengths is output from the output ports 3,4,5,6, respectively.
And when lambda is 1 ,λ 2 ,λ 3 ,λ 4 When light is input from the input port 5, light is output from the output ports 2 to 5, respectively, and in order to achieve the purpose that light output from the output port 6 is wavelength 1, it is found from the table that λ1 can be input from the input port 6, output from the output port 1, and λ1 can be input from the input port 1 and output from the output port 6 according to symmetry. Then, the input light is split into two beams by a filter having a wavelength range lambda 2 ,λ 3 ,λ 4 Continues to be input from the input port 5, λ 1 Is input from input port 1 and it is output from output port 6.
Similarly, when the wavelength is lambda 1 ,λ 2 ,λ 3 ,λ 4 When the light is inputted from the input port 6, the light is outputted from the output ports 1,2,3,4, and the inputted light is divided into lambda in order to ensure that the light outputted from the output ports 5 and 6 is lambda 1, lambda 2 1 ,λ 2 And lambda (lambda) 3 ,λ 4 Two bundles, lambda 1 ,λ 2 From the input port 2, lambda is known from the data in the table 1 ,λ 2 Will be output from output port 5 and output port 6, respectively, lambda 3 ,λ 4 Is input from the input port 6 and output from the output port 3 and the output port 4.
Similarly, the input light is divided into lambda 1 ,λ 2 ,λ 3 And lambda (lambda) 4 Two bundles are input from the input ports 3 and 7, respectively, and can be output from the output ports 1 to 4 as well.
Compared with a traditional arrayed waveguide grating optical wavelength router with a free spectral range of N channel intervals, the structural design of the invention reduces the loss difference of an output frequency spectrum in two aspects: firstly, because the free spectrum range is larger than the product of the number of channels and the channel interval, the problem that the loss difference is at least 3dB for all output spectrums corresponding to the same input channel is avoided; and secondly, the output frequency spectrums of all the input channels are in m diffraction orders, so that the problem that the loss difference between the center input channel and the edge input channel is at least 3dB is avoided.
The free spectrum range of the array waveguide grating designed by the router structure is larger, so that the loss uniformity is better and the loss difference is small for the central 4 wavelengths, and the aim of outputting spectrum circulation can be achieved through cascading of the input channel and the filter.
Regarding the design of the filter, as shown in fig. 4, the implementation may employ a structure of a cascade mach-zehnder interferometer, which may be a 1×2 or 2×2 lattice filter.
By designing the coupling coefficient of the directional coupler and the arm length difference of each stage Mach-Zehnder interferometer, light with different wavelength ranges and approximately rectangular frequency spectrums can be respectively output on the two output channels. With the increase of cascade level, the output spectrum shape is more and more close to rectangle, so that the input light can be divided into two parts according to the different wavelength ranges without increasing crosstalk and loss.
Fig. 5 is a schematic structural diagram of an arrayed waveguide grating optical wavelength router of the present invention. It can be seen from the structure that when the filter is connected to the input waveguide of the arrayed waveguide grating, the waveguides will cross, and many researches have been made on the design of the cross waveguide structure to solve the problem. With respect to the design of arrayed waveguide gratings, a conventional saddle-shaped structure is used for design as shown in fig. 2.
Embodiments of the invention are as follows:
the invention is further illustrated by the following examples of the invention. The following parameters are assumed: selecting SOI, wherein the thickness of the Si core layer is 220nm, burying the lower packageLayer SiO 2 Is 1 μm thick, upper cladding SiO 2 Is 2 μm thick. The core silicon waveguide has a width of 500nm, which has a relatively good manufacturing tolerance.
Examples: 4 x 4 AWGR with 20nm channel spacing was designed, center wavelength lambda c The designed free spectral range was 80nm for 1550 nm. FIG. 2 is a schematic diagram of the structure, and Table 3 shows the relevant design parameters.
Table 3.4x4 design parameters of AWGR
Under the conventional design, the output spectrograms corresponding to the four input channels shown in fig. 6 can be obtained, wherein (a), (b), (c) and (d) respectively represent the output spectrograms of the input channels 1-4. The input port 2 is a central input channel. And the data analysis is carried out on the spectrograms to obtain the output spectrum center wavelength and the insertion loss corresponding to each input channel and each output channel in the table 4 and the table 5. Since m is approximately rounded, the free spectral range of the m diffraction order obtained by equation (3) is 85.5nm, and not 4×20=80 nm, so it can be seen that when other diffraction orders are used, a relatively large frequency difference occurs, taking input channel 4 as an example, the output 3 and output 4 output spectrums are m+1 diffraction orders, the center wavelengths are respectively shifted by 1510-1506.02 =3.98 nm and 1530-1528.07 =1.93 nm, and the spectrum loss difference of all channels is 8.03-3.70=4.33 dB.
Table 4.4x4 center wavelength of the output spectrum of AWGR
Table 5.4x4 insertion loss of the output spectrum of AWGR
Next, according to the present invention, cascaded mach-zehnder interferometers with different center wavelengths are designed, fig. 4 is a schematic structural diagram, in which a 4-order cascaded mach-zehnder interferometer is used, coupling coefficients of the directional coupler are 0.5,0.13,0.12,0.5,0.25, and arm length differences of each stage are l1=l0, l2=2xl0, l3=2xl0+0.5 xλ, respectively 0 Each of (a) dividing the wavelength range into 1510nm and 1530-1570nm, corresponding to input channel 1 and input channel 5, (b) dividing the wavelength range into 1510nm-1530nm and 1550-1570nm, corresponding to input channel 2 and input channel 6, respectively, and (c) dividing the wavelength range into 1510nm-1550nm and 1570nm, corresponding to input channel 3 and input channel 7, respectively.
Next, an AWG of 7*4 with a channel spacing of 20nm is designed and filters are cascaded in front, fig. 5 is a schematic diagram of a specific structure, the center wavelength λ c The diffraction order m=3 at 1550nm and the free spectral range 313nm. Table 6 is the parameter design.
TABLE 6 design parameters of AWG of the invention
| Center wavelength (nm) | 1550 |
| Number of input channels | 7 |
| Number of output channels | 4 |
| Array wave derivative | 35 |
| Diffraction orders | 3 |
| Flat area length (um) | 25 |
| Input waveguide/output waveguide spacing (um) | 1.8 |
| Array waveguide spacing (um) | 1.8 |
| Array waveguide length difference (um) | 6.96 |
The output spectra corresponding to the four input channels shown in FIG. 8, FIG. 9, FIG. 10, FIG. 11 can be obtained, and FIG. 8 (a) (b) is the output spectra of input channels 3 and 7, respectively, λ 1 ，λ 2 ，λ 3 Input from input channel 3 and output from output channels 4,5,6, lambda 4 Since the output spectrum is inputted from the input channel 7 and outputted from the output channel 3, the output spectrum is obtained from the output channels 3-6, and similarly, fig. 10 (a) and (b) are the output spectra of the input channels 5 and 2, respectively, and fig. 11 (a) and (b) are the output spectra of the input channels 6 and 1, respectively. FIG. 9 is an output spectrum of the input channel 4 because the center input channel 4 does not require a cascaded Mach-Zehnder interferometer and can directly output λ at the output channels 3-6 1 ，λ 2 ，λ 3 ，λ 4 Is a frequency spectrum of (c).
The input channel 4 is a central input channel. And the data analysis is carried out on the spectrograms to obtain the table 6 and the table 7, namely the central wavelength and the insertion loss of the output frequency spectrum corresponding to each input channel and each output channel. Because the free spectral range is large, only the output spectrum with the diffraction order of m is used, the frequency difference is small, the maximum frequency difference is 0.58nm, and the channel interval is 20nm, so that the output spectrum is negligible. And the spectrum loss of all channels is different as follows
4.54-3.83=0.71 dB, which is approximately one sixth of the spectral difference of 4.33dB of the conventional design described above.
TABLE 6 output spectral center wavelength of AWG router of the invention
TABLE 7 output spectral insertion loss of AWG router of the invention
From the above embodiments, it can be seen that by adopting the method of the present invention, the output spectrum difference of the AWG router can be reduced to less than 1dB, and the effect of reducing the frequency difference can also be achieved.
The foregoing description is only illustrative of the present invention and is not intended to limit the scope of the invention, and all equivalent structures or equivalent processes or direct or indirect application in other related technical fields are included in the scope of the present invention.
Claims (6)
1. An AWG router with a filter and an input channel cascaded to realize spectrum uniformity, which is characterized in that: the filter comprises N filtering input waveguides (01), N-1 filters (02), 2N-1 AWG input waveguides (03), an arrayed waveguide grating (04) and N output waveguides (05); the free spectral range is larger than the 2 XN times channel wavelength interval in the array waveguide grating (04), the array waveguide grating (04) is provided with 2N-1 input/output channels, and the central input port of the array waveguide grating (04) is connected with the 1 st filtering input waveguide (01) through an AWG input waveguide (03); for other input ports except a central input port in the array waveguide grating, an nth input port and an n+nth input port form a group of input ports, the N input ports and the n+nth input ports are respectively connected to the output ends of the same filter (02) through respective AWG input waveguides (03), the total N-1 group of input ports are connected to N-1 filters (02), and the input ends of the N-1 filters (02) are respectively connected with the rest N-1 filter input waveguides (01).
2. The AWG router of claim 1, wherein the filter and input channel cascade achieves spectral uniformity, wherein: the filter (02) is a 1×2 filter, and the input light is subjected to spectral processing.
3. The AWG router of claim 1, wherein the filter and input channel cascade achieves spectral uniformity, wherein: n light in the middle wavelength in the diffraction order wavelength range is input into N filtering input waveguides (01) and then enters an array waveguide grating (02), light input from the rest N-1 filtering input waveguides (01) except the 1 st filtering input waveguide (01) is split into two light beams with different wavelengths through respective filters, then the two light beams enter two input channels of the array waveguide grating (04) respectively, and then the two light beams are output from an output waveguide (05) after being routed through the wavelengths of the array waveguide grating (04).
4. The AWG router of claim 1, wherein the filter and input channel cascade achieves spectral uniformity, wherein: the Array Waveguide Grating (AWG) mainly comprises an input slab waveguide area, an array waveguide area and an output slab waveguide area which are sequentially arranged from input to output, wherein the array waveguide area is positioned between the input slab waveguide area and the output slab waveguide area.
5. The AWG router of claim 1, wherein the filter and input channel cascade achieves spectral uniformity, wherein: the input ports except the central input port of the array waveguide grating (02) are input by adopting a 1 multiplied by 2 filter and cascading two AWG input waveguides (03), so that when the output frequency spectrum corresponding to a part of light with a certain wavelength does not meet the AWG wavelength routing condition after the original input light is input to the corresponding channel of the array waveguide grating (02), the part of light with the certain wavelength in the original input light is introduced into another input channel except the corresponding channel of the array waveguide grating (02) according to the wavelength routing relation inside the array waveguide grating (02), and then all the output frequency spectrums of the original input light input to the array waveguide grating (02) meet the array waveguide grating (02) wavelength routing condition, so that the function of wavelength routing is realized.
6. The AWG router of claim 1, wherein the filter and input channel cascade achieves spectral uniformity, wherein: the filter adopts a cascade Mach-Zehnder interferometer structure.
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| JP2005003832A (en) * | 2003-06-11 | 2005-01-06 | Nippon Telegr & Teleph Corp <Ntt> | Optical wavelength-multiplex-demultiplex device |
| CN105137544A (en) * | 2015-10-15 | 2015-12-09 | 中国科学院半导体研究所 | Non-blocking wavelength selective optical waveguide switch |
| CN106612154A (en) * | 2015-10-26 | 2017-05-03 | 华为技术有限公司 | Optical transmission method and optical transmission device |
| CN208351042U (en) * | 2018-05-22 | 2019-01-08 | 浙江大学 | The uniform AWG router of frequency spectrum is realized in a kind of filter and input channel cascade |
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| JP2005003832A (en) * | 2003-06-11 | 2005-01-06 | Nippon Telegr & Teleph Corp <Ntt> | Optical wavelength-multiplex-demultiplex device |
| CN105137544A (en) * | 2015-10-15 | 2015-12-09 | 中国科学院半导体研究所 | Non-blocking wavelength selective optical waveguide switch |
| CN106612154A (en) * | 2015-10-26 | 2017-05-03 | 华为技术有限公司 | Optical transmission method and optical transmission device |
| CN208351042U (en) * | 2018-05-22 | 2019-01-08 | 浙江大学 | The uniform AWG router of frequency spectrum is realized in a kind of filter and input channel cascade |
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