TW200411242A - Arrayed waveguide gratings for WDM - Google Patents

Abstract

The arrayed waveguide grating (AWG) is the most potential and developmental devices in wavelength division multiplexing (WDM) of optical communication system. This petition is focus on designing AWG that has specially structure. First, using a taper structure in AWG input and output waveguide of free propagation range (FPR), the spectrum response becomes flat and the error of wavelength shift which is influenced by temperature and polarization is tolerated, the crosstalk and insertion loss have be reduced about 2~4dB. In addition, the performance of AWG will be better than classical one by using both multimode interference (MMI) and taper structure of AWG.

Description

200411242 [Technology of the Sun, Moon, and Households] The present invention is a 1 multiplexer, and here it is; a type of demultiplexing of the array waveguide grating type in optical fiber communication, and 2 changes in 5 Part of the waveguide structure gives a special change to stabilize the external environment: ΐ can improve the AWG's skin performance λ amplitude, which is beneficial to the heart and stomach and reduces packaging costs. [Previous technology] Due to the rapid development of ', Kushiro Bayou, people's needs for data transmission (^ A) At this point, optical fiber networks are also increasingly moving towards large-capacity, changeable, fixed, and cost-effective aspects. In addition, the gradual formation of the optical fiber network architecture makes research and manufacturing of optical fiber communication components increasingly important, and cooperates with different multiplexing technologies to transmit optical signals and provide faster and wider services. 1987, United States Donald et al. Of the Naval Institute first proposed the concept of a planar waveguide combined with a planar grating, and applied for a US patent US 4 6 9 6 5 3 6. 1950, Lucent Corporation Dragon et al. al · Proposed the use of NxN waveguides as components of spectral power. 丨 In 1992, Lucent filed a US patent case US 5136671 again. Using different lengths of waveguides, the optical path difference fixed the phase difference at the exit end of the waveguide and was successful. Nowadays, the widely used fiber-optic components of the split-wave multiplexing system of the arrayed waveguide grating type are used today, and subsequent related patent applications for AWG improvement have been successively issued. China's patent case 428113 proposes that the AWG array waveguide is processed into a special design, which can reduce unwanted noise in the spectrum and improve the isolation of the signal. Further, the temperature and polarization state can be controlled by modulation to the wavelength drift. . Array Wave 'Optical: iArrayed

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200411242 V. Description of Invention (2)

Waveguide Gratings (AWG) type passive components have the most potential and development space. 2. Arrayed Waveguide

GratingS: AWG) is a process that uses semiconductor process technology to etch features on waveguides.

The special geometric structure, a six-inch wafer can etch about six AWG structures, and then after cutting, packaging, testing and other steps and finally application and production, the use of this waveguide structure can be used in optical fiber communication passive The component achieves the purpose of component wavelength signal-signal. The AWG principle uses a fixed difference in the optical path of each adjacent array waveguide, and uses grating diffraction and interference to achieve the demultiplexing function. The AWG can demultiplex multiple signals at different wavelengths at the same time, making the cost per channel lower than that of other WDM components, and the performance of the AWG component is better than that of other components. Generally, the crosstalk interference of AWG demultiplexing components is about -2 5dB ~ -30 dB, and the insertion loss is about -5dB. The higher the channel output ’, the smaller the channel spacing will degrade its performance. [Summary] "Technical Problems to Be Solved"

Although AWG technology has strong demultiplexing capability, many channels, and low cost, it has certain difficulties and accuracy requirements in the process and packaging. In the process, the structure to be etched is very complicated, and the accuracy of the process is very difficult. In addition: under the influence of oldness and polarization state, it will often cause unpredictable wavelength drift. :: The system cannot reach the correct wavelength signal, or even the signal can not be blocked. Take the specifications of 100 GHz and 32 channels as an example. The temperature tolerance range is ~ 65 ° C and the wavelength drift is about 0.001nm / t. With a channel spacing of only 0 ^, a slight wavelength drift will make the receiving photodetector unable to distinguish,

200411242 V. Description of the invention (3) A $ pair also makes the cost of the AWG relatively increase, so it is necessary to flatten the output channel Λ number. In addition, high-density and high-channel AWGs also have problems such as excessive crosstalk interference and insertion loss. "Technical means to solve the problem" # This invention uses the AWG element optical signal to propagate through the waveguide, giving the original 鈇 $ waveguide a special modified structure, which can be multi-mode interfered by the cone-shaped structure and its MMI type I 丄. Characteristics, to achieve the AWG split-wave to, good state of the split-wave performance, in which the purpose of the MM 1 structure is to manufacture the characteristics of lx N splitting, to achieve the effect of J-like multi-grating enhancement. "Effects of the previous technology" Six rounds of force, f is used to improve the transmission rate of the system by using the special structure of the cone mouth area distribution ', and proposed the use of multi-modal interference technology plus the cone mouth, 纟 σ The structured arrayed waveguide grating, compared with the general structure of the AWG system that can obtain more two-wave characteristics, includes the improvement of loss and crosstalk interference and the flattening requirements of the forced output signal. [Embodiment] Figure 1 is the structure diagram of a simple AWG sub-wavelength component. An array waveguide 2 'with different degrees is connected to a waveguide base. The input and output optical signal ends are both connected directly. Optical fiber transmission line 'The main structure of the MG demultiplexing element is an array waveguide 2 (Ar r ay Wavegu i de aka Pharsar rr ay), an input waveguide 5 and an output that connect input and output fiber signals at both ends

200411242 V. Description of the invention (4) Waveguide 6 (1/0 Waveguide), and Free Propagation Range 3, 7 (Free Propagation Range; FPR) of grating diffraction, interference, and coupling. The main component of the AWG is this Three major sections. In Figure 2, the principle of AWG's demultiplexing is that when the light wave signal enters the shank from the optical fiber; after it is combined with the input waveguide end 4, the optical signal will follow the input waveguide to reach the input end of the free end of the free end coupling region. The input 8 in the free coupling area of the input end is evenly diverged to the receiver 9 in the free coupling area of the input end, and the uniform input light enters the array waveguide 2. In the array waveguide 2, the light waves propagate along the respective array waveguide 2 to the output. The transmitting end 10 of the free coupling region 7 at the end, because the array waveguide _ a waveguide optical path travels different lengths, resulting in different optical paths of the respective waveguide light waves, so that the output end of the free coupling region 7 at the transmitting end Generated optical path difference and phase angle difference 'Finally the light has interference and diffraction phenomena in the free-coupling region 7 at the output end' The different positions of the light with different wavelengths due to the phase difference are also constructively strengthened The point is at the receiving end 11 of the free area 7 of the output end, which controls the position of the output waveguide 6 and can receive different wavelengths; by design, the optical field is enhanced to couple the optical signal to the fiber. First, take a channel spacing of 200GHz, 8 channels as clean, as an example, l-wave passive components, the main material of the material is dioxide; delay and hope that the light field transmission of the components can basically be a single V) Set the AWG waveguide core 13 (core) and the waveguide to propagate in the same way, because the equivalent refractive index is shown in Figure 3, _ns points: 乂 / 2⑹cg) The difference ratio of the ratio is 0 _ 6 8%, Fabricated on a silicon substrate of about 3 cm x 2 cm

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200411242 V. Description of the invention (5) The waveguide structure with a basic width of 4 // m, the actual center wavelength is 1.55 β m for the C band for general communication, and the operating wavelength range set for analysis is 1.54 ~ 1.56 μm, after the analysis, the analysis of the output spectrum is shown in Figure 4. The insertion loss is about 4.93dB, the non-uniformity is about 0.5 (1β, and the flatness of the output signal 1 is -1 〇d. B is about 1.1 nm. One aspect of the present invention is to add this part in the free-coupling region 7 of the AWG output end and the free-combination region 3 of the wheel-in end. " " The mouth structure 1 4 and the tapered mouth structure 14 are shown in Figure 5 in the AWG. The length 1 of the tapered mouth 1 is set to 1 0 0 0 // m to avoid excess waveguide loss, and the tapered The function of the notch structure ^ can receive more light fields according to the incident direction of the AWG light field, so that each: m can receive more signals of other wavelengths' or put :, the role of the light field, and, The purpose is to flatten the frequency signal and control the cost between (Shi ft) and accuracy, and to receive more light fields and reduce You Gonghan-In order to compare the conventional arrayed waveguide gratings of the conventional technology, the present embodiment also uses AW X of 2 0GHZ, 8-channel signal output to take nc # ns ^^ input and output free coupling zone 3, The A WG with the emission ends 8, 10 and 7 at the receiving end of Q 7 at 1 0 / zm gives a stop of 4 m. The opening / mouth width is approximately uj, which is 0.5 nm flatter than the signal in the Λ out-spectrum spectrum, and The AWG of the plug structure is increased by about 7 and the lost-to-know ratio is reduced by about 3dB compared with the conventional technology.

Page 9 200411242 V. Description of the invention (6) In addition, the excess wave packet interference in the spectrum response is also reduced by about 1 OdB due to the special structure of the tapered port. The width of the tapered opening is 16 and the size of the distribution area and the degree of flattening. It has a direct relationship with the characteristics of component insertion loss and wave packet interference. The analysis in Figures 7 and 8 shows that the width of the tapered opening is 16 The effect of the size and distribution area on the demultiplexing characteristics of the AWG · element. When the width of the tapered port is 16 wider, the degree of planarization is better, and the insertion loss is relatively reduced. The more the distribution area is, the more the planarization is. The degree is also proportional to the insertion loss. On the other hand, in the conventional technology, increasing the number of array waveguides 2 and the number of input waveguides 5 and output waveguides 6 of the AWG demultiplexer can reduce the insertion loss and crosstalk interference. However, the general geometric structure of AWG The number of arrayed waveguides 2 cannot be increased arbitrarily, and an excessive number of arrayed waveguides will cause difficulties in the manufacturing process and the waveguide coupling loss and bending loss between the arrayed waveguides 2. In view of this, the present invention transforms the tapered port structure into a multimode interference (MMI) 1 7 structure, as shown in FIG. 9 'multimode evil interference waveguide structure 17-like a cone The basic role of the mouth, but because its opening shows a drastic change, it will bow into the generation of multi-modes when light waves are transmitted, and the multi-modes will interfere with each other in the MMI cavity region 17 and Γ makes this MM The structure of the I-waveguide 17 produces spectroscopic characteristics, and the length of the MM j ^ guide 17 can be appropriately controlled to achieve a specific 1 × N beam-splitting effect. The present invention deforms the MM I special structure 1 7 to simulate AWG as Multi-diffraction diffraction enhancement, which improves the AWG's demultiplexing performance and also contains the effect of flattening the output spectrum

200411242 V. Description of the invention (7) Fruits exist. The MMI structure 17 in the preferred embodiment has a width of 10 / zm and a length of 475 # m. As shown in Fig. 10, it is analyzed as a lx 2 sub-wave structure, and the best embodiment applied to the AWG sub-wave multiplexer is A special structure 17 of this MMI is given on the exit-side waveguides 8, 1 (T in the free coupling region of the AWG, and a tapered-port structure 14 is given on the receiving-end waveguides 9, 11. Structure 14 includes a waveguide with a narrow waveguide width and a waveguide with a wide waveguide width. The width of the waveguide varies with the length increasing or decreasing. This new structure can not only reduce the loss by collecting light field characteristics of the tapered mouth, but also 5dB ， 而 ， The spectral characteristics of the MM I structure can be used to achieve the function of improving crosstalk interference and spectral flattening. After analysis, its spectral output is shown in Figure XI, the insertion loss of this new structure AWG is about 1. 5dB, and The adjacent channel output crosstalk interference is about -35dB, which is about 5dB higher than the crosstalk interference in the conventional technology. The MMI structure device may include a waveguide with a narrow waveguide width and a waveguide with a wide waveguide width. The width does not change with the length A special device that produces a multi-mode effect and controls its length to further adjust the multi-modal interference-enhancing position. Another modified new structure of the present invention, that is, as shown in FIG. 12, a traditional Y-waveguide can be used 18 (Y-branch) or lx N branch spectroscopic structure instead of lx 2 or lx N MM I spectroscopic structure 17 can be expected to be easier in manufacturing process than rectangular MMI structure 17 and light wave The propagation loss of the waveguide is also smaller than that of the MM I waveguide structure 17. In addition, according to the spectral characteristics of the MM I structure 17 or the tapered opening structure 14, it is possible to

200411242 V. Description of the invention (8) The use of modulation technology such as electro-optic to control the refractive index change of the area, using different carriers in any part of the transmitting and receiving ends of the free coupling area of the input end and the free coupling area of the output end Optical modulation such as concentration or electro-optic modulation controls its optical characteristics and refractive index changes, and further adjusts the special structure of the MMI or tapered port effect to improve its optical characteristics and the effect of the center wavelength, thereby controlling M Optical properties or spectral effects, to achieve the purpose of modulating AWG, make this system more _ add adjustable flexibility.

Page 12 200411242 Brief description of the diagram Figure 1 is a simple device description of a common AWG demultiplexer for optical fiber communication. Figure 2 shows the detailed structure of the AWG demultiplexer and its effect. Figure 3 is a schematic diagram of a 3D waveguide structure, including the core and cladding channel structures. Figure 4 is the output spectrum of an AWG demultiplexer with 8 GHz output at 200 GHz. Figure 5 is a structural diagram of the AWG sub-wave multiplexer with a tapered port output device installed in the free coupling area. Fig. 6 is a detailed structural diagram of a tapered port device. Figure 7 shows an AWG output spectrum chart with 200 GHz, 8-channel output and a tapered port structure. Figure 8 is the analysis of the effect of different tapered mouth widths on the flattening width of the spectral response, and comparisons for different polarization directions. Figure 9 is an analysis of the flattening width effect and insertion loss evaluation of the time-aligned system when the tapered port structure exists in different numbers of AWG regions. Figure 10 is a detailed structural diagram of an MMI device. Figure 11 shows a spectral effect of lx 2 generated by the MMI device in the optical waveguide. Figure 12 shows an AWG output spectrum chart at 2000 GHz, 8-channel output, and using both the MMI structure and the tapered port structure. Figure 13 shows a Y-branch spectral waveguide. An effect of this type of spectral waveguide can be used instead of MEMS.

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Claims (1)

200411242 6. Scope of patent application 1. An arrayed waveguide grating demultiplexer having a structure including: one or more input waveguides; a free coupling region at an input end connected to the input waveguide so that light waves are at the input end Uniform diffusion in the free coupling region; an array waveguide of unequal length of adjacent waveguides is connected to the free Kuma junction region of the input end, and a free coupling region of the output end is connected to the array waveguide so that the light waves A splitting effect is generated in the free-coupling region of the output end; two or more output waveguides are connected to the free-coupling region of the output end to guide light waves out of the waveguide and output signals. 2. The arrayed waveguide grating wavelength division multiplexer according to item 1 of the scope of patent application, which further includes giving a cone to any part of the transmitting end and the receiving end of the free coupling region of the input end and the free coupling region of the output end. Shaped special structure. 3. The arrayed waveguide grating demultiplexer according to item 2 of the scope of patent application, wherein the special structure of the tapered opening includes a waveguide with a narrow waveguide width and a waveguide with a wide waveguide width, and the width of the waveguide varies with the length Increment or decrement and change 4. According to the arrayed waveguide grating demultiplexer described in item 1 of the scope of the patent application, it further includes any part of the transmitting end and the receiving end in the free coupling area of the input end and the free coupling area of the output end. MM I effect Page 14 200411242 VI. Special structure device with patent application scope. 5. According to the array waveguide grating demultiplexer described in item 4 of the scope of the patent application, the MM I structure device includes a waveguide with a narrow waveguide width and a waveguide ~ a wide waveguide, and the width does not change with the length. , A special device that generates multi-mode effects, and controls its length to further adjust the position of multi-modal interference enhancement. 6. The arrayed waveguide grating demultiplexer according to item 1 of the scope of the patent application, which further includes a point at any one of the transmitting end and the receiving end in the free coupling area of the input end and the free coupling area of the output end. The device of the cross-waveguide achieves the purpose of demultiplexing. 7. According to the arrayed waveguide grating demultiplexer described in item 6 of the scope of the patent application, the device of the bifurcated waveguide includes various Y, X-division, etc. demultiplexing devices and changes using related optical modulation methods The effect of its spectral characteristics. 8. According to the array waveguide grating demultiplexer according to one of the items 2 to 7 of the scope of the patent application, it can be any part of the transmitting end and the receiving end of the free coupling region at the input end and the free coupling region at the output end. The optical properties and refractive index changes are controlled by using optical modulation methods such as doping different carrier concentrations or electro-optic modulation. Page 680