HYBRID MICROOPTICAL WDM RECEIVER FOR PON COMMUNICATION

Transcription

1 VOLUME: 0 NUMBER: 0 JUNE HYBRID MICROOPTICAL WDM RECEIVER FOR PON COMMUNICATION Viezslav JERABEK, Julio ARMAS, Vaclav PRAJZLER Deparmen of Microelecronics, Faculy of Elecrical Engineering, Czech Technical Universiy in Prague, Technicka, 66 7 Prague, Czech Republic jerabek@fel.cvu.cz, armas@fel.cvu.cz, prajzler@fel.cvu.cz Absrac. The paper presens he design, simulaion and consrucion resuls of he wavelengh division muliplex (WDM) opical hybrid receiver module for he passive opical nework (PON). The opical WDM receiver was consruced using sysem of hree micromodules in he new circle opology. The opical micromodule conains mulimode fiber pigail 50/5 µm, VHGT filer wih collimaion lens and wo microwave opoelecronics receiver micromodules (OE receiver micromodules). OE receiver micromodules were designed by use small signal equivalen elecrical circui model and noise model, from which he mahemaically solved he ransmiance funcion, which was used for calculaion and simulaion of he opimal frequency characerisics and signal o noise raio. For deermine he limi frequency of OE receiver micromodule, he ranscenden equaion wih ransmiance funcion was numerically solved. OE receiver micromodule was composed of decollimaion lenses and microwave opoelecronics receivers wih bandwidh,5 GHz and alernaively in SMD echnology wih bandwidh,5 GHz, using he hin layer hybrid echnology. WDM receiver use radiaion 490 nm for inerne and 550 nm for digial TV signals download informaion. inegraed lighwave circuis (MLC) and planar inegraed lighwave circuis (PLC) by combining componens wih passive funcion (opical fiber, lens, VHGT (volume holographic graing riplexer), planar opical waveguides and acive opoelecronics devices (laser diodes, opical amplifiers and phoodiodes) hybridized on one subsrae for collimaing, focusing, imaging, branching, receiving and ransmiing of an opical beams [], []. WDM receiver, Fig., was consruced by using sysem of hree micromodules se on he subsrae in he new circle opology [3]. The opical demuliplexing micromodule is creaed by mulimode opical fiber, collimaing lens and volume holographic graing riplexer diffracion filer (VHGT) [4] and he wo ype microwave opoelecronic receiver micromodules (OE receiver micromodules) wih bandwidh,5 GHz or,5 GHz. In he OE receiver micromodules, each diffraced beam from VHGT was focused on he acive area of PIN phoodeecor (PIN PD) conneced o microwave amplifier. The microopical WDM receiver sysem will be assembled in DIL case. Keywords Collimaing lens, microopical hybrid inegraion, Volume holographic graing riplexer, WDM Receiver.. Inroducion The micromodules for WDM receiver are considered o be he key componen for realizing fiber-o-he-home neworks. Especially an opical WDM Receiver module, ha can receive a 490 nm download daa as well as a 550 nm download video signals for cable TV applicaions. A microopical lighwave hybrid inegraion echnology enables us o consruc a microopical Fig. : WDM Receiver opical sysem wih VHGT.. Sysem Design and Measuremen of Opical Micromodule The OE micromodule is represened by he block diagram 0 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 95

2 VOLUME: 0 NUMBER: 0 JUNE shown in Fig.. A special cylindrical lens is used in he WDM receiver o collimae he beam before he VHGT. The VHGT surface is covered anireflecion layers. The collimaed beam is diffraced by he VHGT and focused on he acive area of PIN phoodiodes by collimaion lenses. The PIN PD convers he received opical power of he radiaion ino a phoocurren [5]. We analyze he opical sysem and calculae parameers of he opical micromodules - focal lenghs and inserion losses of he lenses, angles of diffracion, diffracion efficiency, diffracion crossalk on he VHGT for he wavelenghs 490 nm and 550 nm. Fig. : Block diagram of WDM receiver signal pah... Analyses of Opical Collimaing/ Focusing Sysem WDM receiver high efficiency opical sysem uses collimaing/focusing lenses for opical processing of he beam and spo ransformaion. The radiaion propagaes from he muli mode fiber (MMF) across he firs collimaing lens, VGHT and focusing lenses on he acive area of he PIN PD s conneced by microsrip elecrical waveguides o he inpu of he elecronic amplifiers. The main parameers of he sysem were he opical angles, focal disance of he lenses and he diameer of he beam spos, which had a significan influence on VHGT opical characerisics (diffracion efficiency, opical crossalks, sensiiviy ec.). The opical analysis by ray-ransfer marix describes opical sysems in he paraxial approximaion. The ray-ransfer marix (S ) is used in order o find simple and explici expressions for deerminaion of he beam opimal srucural parameers of he focusing sysem. The modal field profiles in he MMF and collimaing lenses are assumed, o be circular symmeric and Gaussian and consider he propagaion of a ray in a homogeneous medium [6]. The schema of he collimaing sysem composed of he MMF and he collimaing lens is shown in Fig. 3. The ray ransfer marix (S ) of he collimaing lens was calculaed as he muliplicaion of he ranslaion marix T and he refracion marices M and M shown in formulas (), () and (3). S S, () M T M 0 L 0 S n n, () n R 0 R P P P P P A P C where P, P and are defined by (4), (5) and (6). P P n B, (3) D, (4) R n, (5) R L n. (6) The focal plane of he collimaing lens is defined by (7). 0 in b A B y, (7) ou 0 C D 0 his implied ha 0 A b C y in, (8) herefore A b, (9) C where b is he fron focal disance FFD of he lens defined by (0), ou is oupu angle and y in is he inpu radial posiion of he ray. P FFD b. (0) P P P P The parameers of he opical sysem are: L = 3,0 mm, R =,3 mm, R = (he concave radius of curvaure of lens back surface). The calculaed values of FFD and aenuaion in he collimaing lens due o Fresnel reflecion a he inerfaces A F for differen wavelengh are shown in he Tab.. Tab.: The calculaed values of he collimaing lenses and opical aenuaion for he wavelengh 30, 490 and 550 nm. λ [nm] n FFD [mm] A F. [db] 550,4865,493 0, ,4870,488 0, ,4885,476 0,349 Fig. 3: Collimaion sysem: MMF-cylindrical lens L. (FFD fron focal disance, L - lengh of he collimaing lens, R, R - radius of curvaure of he lens, n - refracive index, f focal lengh, θ angle of numerical aperure. The decollimaion lens in he opoelecronic micromodule is o provide opimal radiaion focus of he diffraced beam on he acive space of PIN PD. 0 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 96

3 VOLUME: 0 NUMBER: 0 JUNE The radio y of he beam exposiion o he acive area of PIN PD depends on he disance z beween he decollimaion lens PIN PD and he diameer of he beam D(0). Wih he formula (), we obain he radio of he acive area covered. 0 D 0 D y m z q z, () FFD where: y is he radio of he acive area, m is he slope of a line, q is he diameer of he beam a z = 0 mm, D(0)/ is he half diameer of he beam a z = 0 mm. To cover all he acive area of he PIN PD he disance beween he decollimaion lens and PIN PD dependence is shown in Fig. 4. diffracion order [4] as (3). n D B sin, (3) B cos n where n is he Bragg-mached inciden angle in he medium, n is graing srengh refracion index modulaion, D is he hickness of he graing, and B is he Bragg wavelengh. For he compromise posiion of boh graings VHGT sysems, he diffracion efficiencies were calculaed as 7,0 % and 74,9 % for 550 nm and 490 nm respecively. The space disribuion of VHGT opical beams are shown in Fig. 5 and he measured values are shown in Tab.. Fig. 4: Half beam diameer D(0)/ in funcion of disance z. For he focusing process, i was imporan o analyze he acive area of he PIN PD covering by he radiaion cone, formed behind focusing lens. For he diameer acive area D = 40 µm of PIN PD was calculaed and measured disance from he focusing lens FFD =,34 mm... Analysis and Measuremen of VHGT For he opical demuliplex of he wavelengh 490 nm and 550 nm opical beam in WDM receiver was in he opical micromodule used he VHGT filer from Ondax Ld. wih double graing sysem. This ransmission ype graing filers has high diffracion efficiency, very low inserion loses and opical crossalk. The Bragg diffracion condiion is given by () diff sin, () B where Λ is Bragg consan, B is he Bragg wavelengh, θ diff is he diffracion angle. From Eq. () were deermined Bragg consans of VHGT by use measuremen of he diffrac angle. The Bragg consan Λ = 4,66 µm and Λ = 4,67 µm was calculaed, where θ diff = 8,4 for λ = 490 nm and θ diff = 9, o for λ =550 nm. The Bragg diffracion efficiency B for VHGT was defined as he raio beween he diffraced inensiy and he inciden inensiy, wihou considering absorpion and Fresnel reflecions a he inerfaces. When he Bragg condiion is saisfied for wavelengh B, he diffracion efficiency B is given for ransmission graings firs Fig. 5: The diffraced beams wih crossalk a wavelengh = 550 nm and = 490 nm. Tab.: The measured diffracion efficiency B and diffracion losses A F of he VHGT. λ [nm] P IN [μw] P D [μw] B [%] A F [db] ,7 73,, ,0,4 Where P IN is inciden opical power, P D is diffraced opical power and A F [db] is he aenuaion in he VHGT due o non diffraced beam and crossalk. The aenuaion in he VHGT due o Fresnel reflecion a he inerfaces is very low because he VHGT has anireflecion coaed surfaces. By he measuremen, he space disribuion of an opical power was invesigaed ha in he cener of diagram Fig. 5, exis wo peaks of radiaion no diffraced, which don equal of Bragg condiion. These radiaions have o be filered, when VHGT will be used in hree wavelengh WDM receiver or ransceiver. A he opposie side of he space disribuion power diagram is clear percepible peaks diffraced o he opposie direcion as opical crossalk. In he nex measuremen of opical crossalk was used he formula (4). P A 0 log, (4) P where P λ is he is he opical diffraced power, P λ is opical power second wavelengh, diffraced a he same direcion han P λ. The minimal opical crossalk of he opical beams for wo wavelenghs was very imporan requiremen for 0 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 97

4 VOLUME: 0 NUMBER: 0 JUNE he good BER (bi error rae). The opical crossalk was given by opical power, which was diffraced o wavelengh opposie direcion. For BER = 0-9 i was needed opical crossalk aenuaion A λ > db. The opical crossalk P λ for he wavelengh λ =490 and λ = 550 nm wih he oal power normalized o P IN = 360 µw was measured. I correspond A λ = 8,9 db and,44 db as is shown in Tab. 3. Tab.3: The opical crossalk of he VHGT beams measuremen. Diffraced λ Toal Power Crossalk Power A [nm] P IN [μw] P P λ [μw] λ [µw] λ [db] , , ,9 For measuremen of he opical power space disribuion in D or 3D was used beam profiler head BP 04 IR from Thorlabs wih special sofware. The crossalk measuremen show us ha using he VHGT is possible diffrac wo beams a he same ime wihou undesired effec from each oher. OE receiver micromodules, he elecro/opical ransmission, dynamic response and noise figure characerisics parameers were designed and measured. The low impedance OE receiver was composed of he InGaAs PIN phoodeecor C3066 ECER wih bandwidh 3,5 GHz and HBT monolihic amplifier HM 396 made by GaAs/ InGaP heerojuncion bipolar ransisors echnology (HBT) wih bandwidh 8GHz and gain 0 db. In microwave signal pah was used a microsrip waveguide, connecing he PIN PD o he signal inpu of HBT amplifier. The hin film Au microsrip waveguides was formed by a sandard lihographic spuering process assembly on an alumina subsrae, in which he passive and acive componens in chip form are mouned direcly on Au srip waveguide lines and fix by epoek. The parameers of WDM receiver were calculaed and measured. The low frequency ransmiances were 40 V/W and 70 V/W for low and ransimpedance OE receivers respecively. The dynamic measuremen resuls of modulaion frequency characerisic OE receivers, f T =,5 GHz for low impedance OE receiver and f T =,5 GHz for ransimpedance OE receiver as is shown in Fig Sysem Design and Measuremen of OE Receiver Micromodules For OE receiver micromodules were used wo ypes of he OE receivers. For consrucion of he,5 GHz opoelecronic microwave micromodules wih ransimpedance OE receiver was used SMD echnology, which is sufficien for his dynamics response devices. OE receivers were designed by use small signal equivalen elecrical circui model and noise model. The inernal srucure of he ransimpedance OE receiver, wih he ATF-3663 amplifier, InGaAs PIN phoodiode and he bias circuiry is presened in Fig. 6. All componens - PIN PD, capaciors, resisors and inducance in SMD package were assembled on composie low loss subsrae (Rodgers), wih Au/ Cu microsrip line and waveguide moive. The focusing lens was fixed on Au/ Cu currier in fron of PIN PD. Fig. 6: Design and consrucion of OE receiver micromodule. A) The elecrical schema of he ransimpedance OE receiver B) The real microwave opoelecronic micromodule assembly. Fig. 7: The measured scaering parameer S frequency characerisics of he OE receiver for low impedance and ransimpedance amplifier. The signal o noise raio (SNR) of WDM receiver was calculaed and measured for boh ype of OE receivers. In he case of he ransimpedance OE receiver was measured SNR = 7,3 db and in he case of he low impedance OE receiver SNR = 3,6 db. This corresponds wih opical aenuaion reserves 5,7 db for ransimpedance and db for low impedance OE receiver. We presume SM fiber wih an opical loss 0, db/km and SNR =,6 db for BER = 0-9. These values correspond o he ransmission disance of he 8,5 km or 0 km opical SM fiber. When we subrac opical losses,4 db of he opical demuliplexing and imagin sysem of WDM receiver, he ransmi disance drop o,5 km or 3 km of opical SM fiber respecively. The WDM receiver Rx has been consruced using sysem of hree micromodules in he new circle opology se on he alumina or composie subsrae. The fundamenal layou of he hybrid inegraed microopical WDM receiver is given on Fig. 8. The low impedance OE receiver for,5 GHz bandwidh opoelecronic micromodules were realized by he hin layer hybrid inegraion echnology. For realized 0 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 98

5 VOLUME: 0 NUMBER: 0 JUNE Fig. 8: WDM receiver micromodule layou based on microopical hybrid inegraion echnology. Fig. 9: WDM planar hybrid inegraed ransceiver. 4. PLC Hybrid Inegraed WDM Transceiver WDM ransceiver in PLC (Planar Lighwave Circui) hybrid inegraion echnology is shown in Fig. 9. Our work was focused on design an opical par of WDM receiver, which was realized as PLC riplex filer designed by wo sage mulimode inerference or microring resonaor filer, which was made from polymer maerials. For design was used BMP program from R Sof. As polymer we choose NANOTM SU polymer from Micro Chem Corp. due o good opical and mechanical properies (his polymer has opical losses less han db/cm for 300 and 550 nm wavelenghs. The polymer layer was deposied by using spin coaing mehod wih silica on silicon subsrae. Before applicaion of lihography procedure, he samples were prebaked a 90 C for 45 min before a lihography. As a las sep, he pos backing a 90 C for 60 min would be applied. The channel waveguides would be fabricaed by using UV ligh for carried ou of he sabilized opical properies. The phoodeecors and laser in SMD package were placed in he groove for eliminaion heigh offse. The opimum disance among opical waveguides face on base polymer SU8-000 and opical fiber or phoodeecor in he receiving par was specified by BMP program simulaion. The receive opoelecronic par was made same as a microopical ype WDM receiver. The opoelecronic ransmier for λ 3 = 30 nm upsream radiaion uses Fabry-Pero InGaAsP laser diode fix on meallic submoun wih a microwave modulaor and opical average power feedback conrol elecronics. The feedback conrol was realized by ADN 830A inegraed circui from Advance Semiconducor. The opical microisolaor and collimaion lens separae laser diode from nondiffraced radiaion of he VHGT downsream beams. 5. Conclusion The paper presens design a novel opology and echnology soluion of IC microopical hybrid inegraed WDM receiver, composed of he opical and opoelecronic micromodules. The opical micromodule use volume holographic graing riplexer (VHGT) as unique opical muliwavelengh demuliplexing elemen in WDM microsysem. The downsream microopical imagine sysem was verified by consrucion and measuremen of he microopical hybrid inegraed WDM receiver. Very low inserion opical losses and opical crossalk of VHGT elemen imply he high sensiiviy and he ransmi disance of opical SM fiber. Furher work was concenraed on design and consrucion of WDM ransceiver realized by planar lighwave circui hybrid inegraion echnology. The opical par will be solved by polymer or glass inerference filer or microopical resonaors. Acknowledgemens This research has been suppored by gran MPO-TIP FR- TI3/797 and he research program MSM of he Czech Technical Universiy in Prague. References [] KATO, K. and Y. TOHMORI. PLC hybrid inegraion echnology and is applicaion o phoonic componens. IEEE Journal of Seleced Topics in Quanum Elecronics. 000, vol. 6, iss., pp ISSN X. DOI: 0.09/ [] HATTA, T., T. MIYAHARA, N. OKADA, M. ISHIZAKI, M. NAKAJI, E. ISHIMURA and K. MOTOSHIMA. Hybrid Inegraion of Waveguide Phoodiode and Preamplifier IC Using Au Sud Bump. Journal of Lighwave Technology. 006, vol. 4, no. 8, ISSN DOI: 0.09/JLT [3] ARMAS, J., V. JERABEK, K. BUSEK, D. MARES and V. PRAJZLER. Microopical Triplexer Sysem wih High 0 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 99

6 VOLUME: 0 NUMBER: 0 JUNE Efficiency for WDM Hybrid Opoelecronic Receivers. In: Proceedind of he Elecronic Devices and Sysems IMAPS CS Inernaional Conference. Brno: Brno Universiy of Technology, 00, pp ISBN [4] Volume Holographic Graings (VHG). In: Ondax, Inc. [online] Available a: hp:// [5] JUDSON TECHNOLOGIES. PIN PD J-CO-RO 40U: Technical documenaion Available a: hp://pdf.direcindusry.com. [6] MENZEL, R. Phoonics. Berlin: Springer, 007. ISBN [7] HAN, Y.-T., Y.-J. PARK, S.-H. PARK, J.-U. SHIN, C.-W. LEE, H. KO, Y. BAEK, C.-H. PARK, Y.-K. KWON, W.-Y. HWANG, K.-R. OH and H. SUNG. Fabricaion of a TFF- Aached WDM-Type Triplex Transceiver Module Using Silica PLC Hybrid Inegraion Technology. Journal of Lighwave Technology. 006, vol. 4, no., pp ISSN DOI: 0.09/JLT Abou Auhors Viezslav JERABEK was born in Prague 95. He received his M Sc and Ph.D. in he Microelecronics from he Czech echnical universiy in Prague 975, and 987. From 005 is head of opoelecronics group a Deparmen of Microelecronics of he Czech Technical Universiy in Prague. His research ineress include planar hybrid inegraed opics and opoelecronics devices, modules and sysems design, echnology and measuremen. Julio ARMAS was born in Ecuador in 973. In 000, he graduaed in Elecronics and elecommunicaions from he Escuela Poliecnica Nacional in Quio Ecuador. He is currenly working as a Ph.D. in he Opoelecronics group. His work is concenraed on he design and consrucion of microwave opoelecronics ransmiers and receivers. Vaclav PRAJZLER was born in 976 in Prague, Czech Republic. In 00 he graduaed from he Faculy of Elecrical Engineering a he Czech Technical Universiy in Prague a Deparmen of Microelecronics. Since 005 he has been working a he Czech Technical Universiy in Prague, Faculy of Elecrical Engineering, Deparmen of Microelecronics as a research fellow. In 007 he obained he Ph.D. degree from he same universiy. His curren research is focused on fabricaion and invesigaion properies of he opical maerials for phoonics and inegraed opics. 0 ADVANCES IN ELECTRICAL AND ELECTRONIC ENGINEERING 00