WDM PON: Systems and Technologies. ECOC workshop Turino, Italy, 2010

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1 WDM PON: Systems and Technologies ECOC workshop Turino, Italy, 2010 Ning Cheng and Frank Effenberger Advanced Technology Department US R&D Center, Huawei Technologies

2 目录 WDM PON Overview WDM PON Technologies System Performance Limitations Summary and Discussions HUAWEI TECHNOLOGIES CO., LTD. Page 2

logical P2P Protocol and data-rate transparency Simple fault

3 WDM PON Systems OLT WDM TRx array ONUs Colorless ONUs 16~32 wavelengths Dedicated bandwidth, guaranteed QoS Physical P2MP, logical P2P Protocol and data-rate transparency Simple fault localization Low ODN Loss Better security HUAWEI TECHNOLOGIES CO., LTD. Page 3

4 WDM PON Applications 4G 4G 3G Enterprise 3G Central Office 2G GPON Residence Broadband service: Residential: Fiber to the home/curb Enterprise: Fiber to the business Backhaul Applications: Mobile backhaul: 2G/3G/4G GPON/EPON backhaul HUAWEI TECHNOLOGIES CO., LTD. Page 4

5 WDM PON Deployment Hancock (USA, 2009) FTTB,field trial 100M/ Small field trials are in Korea, Europe and others No large scale commercial deployment yet. KDDI (2008~2009) WDM-PON field trial Agder (Norway, 2009) FTTH, field trial with 100 lines 100M/ UNET (Netherland, 2009) Business, field trial with 100 lines 100M/ KT (2005~2009) FTTC&FTTH, 150k lines field trial; 100M/ 1.25G/ (TL and wavelength reuse WDM-PON) HUAWEI TECHNOLOGIES CO., LTD. Page 5 Source: FSAN workshop

6 Technology Challenges Colorless ONU is mandatory OAM and inventory issue with colored ONUs Possible colorless ONU solutions: Tunable laser Injection locked FP lasers Reflective semiconductor optical amplifiers Key determining factors Economics: compared to 10G PONs? IL FP Laser Performance: >1Gb/s per lambda and >20km reach Tunable Laser Cost & Performance RSOA HUAWEI TECHNOLOGIES CO., LTD. Page 6

7 目录 WDM PON Overview WDM PON Technologies System Performance Limitations Summary and Discussions HUAWEI TECHNOLOGIES CO., LTD. Page 7

8 Colorless Light Sources Spectrum Sliced Broadband Lightsource LED/SLED/SOA as colorless lightsource Spectrum sliced by for appropriate channels Injection locked FP laser Specially designed FP laser as colorless lightsource FP laser operates on the wavelength of external injected lightwave Reflective Semiconductor Optical Amplifier Semincoductor optical amplifier as lightsource External injected lightwave is amplified, modulated and reflected to CO Using the saturation property of SOA, the downstream wavelength can be used as an injection to SOA and hence reused for upstream transmission Tunable Laser Widely tunable semiconductor laser as colorless lightsource Need protocol to set the operating wavelength HUAWEI TECHNOLOGIES CO., LTD. Page 8

9 Spectrum Slicing ONU CO 1 Advantages 1 2 n-1 n downstream Low cost; no seed light is needed. Disadvantages Filtered spectrum Low bit rate (<155Mb/s), short transmission distance. Because of the low bit rate, spectrum slicing is not a good option for WDM PON upstream 2 n-1 n 1530nm LED or SLED spectrum WDM 1565nm Rx Downstream data Upstream data Tx LED or SLED HUAWEI TECHNOLOGIES CO., LTD. Page 9

10 Tunable Lasers CO WDM ONU Rx TL Advantages No Seed light is needed High bit rate(>2.5gb/s), long transmission distance (~80km) Disadvantages 1 2 n-1 n Very expensive; dynamic wavelength assignment algorithm is needed WDM ONU Rx TL HUAWEI TECHNOLOGIES CO., LTD. Page 10

11 Injection Locked FP Laser ASE seed Broadband Lightsource CO 1530nm 1565nm 1 ONU Advantages Coupler Low cost Disadvantages 1 2 n-1 n downstream Filtered ASE spectrum Seed light is needed Limited bit rate and transmission distance upstream Injection Locked n 2 n-1 WDM Rx Downstream data IL F-P Laser Upstream data Free running spectrum HUAWEI TECHNOLOGIES CO., LTD. Page 11

12 Reflective Semiconductor Optical Amplifiers Broadband Lightsource CO 1530nm ASE seed 1565nm ONU Advantages Coupler Relatively higher bit rate Disadvantages Seed light is needed Limited transmission distance 1 2 n-1 n downstream Filtered ASE spectrum Amplified & reflected output from RSOA WDM Rx RSOA Downstream data RSOA Upstream data mirror HUAWEI TECHNOLOGIES CO., LTD. Page 12

13 Coherent Injection CO Seed source: DFB array DFB DFB DFB DFB WDM Rx Downstream data Upstream data IL F-P Laser Coupler Rx Downstream data Advantages Better performance: higher rate and longer reach WDM RSOA Upstream data Disadvantages DFB array is more expensive than broadband lightsource HUAWEI TECHNOLOGIES CO., LTD. Page 13

14 Self Seeding ONU CO Partial reflection mirror Rx Downstream data Advantages lower cost: without seed Filtered ASE spectrum WDM RSOA Upstream data Disadvantages Poorer performance Amplified & reflected output from RSOA RSOA mirror HUAWEI TECHNOLOGIES CO., LTD. Page 14

Wavelength Reuse ONU CO Rx Downstream data Advantages lower cost: without seed Residue downstream pattern Coupler RSOA Upstream data Disadvantages Erase of downstream pattern is a challenge

15 Wavelength Reuse ONU CO Rx Downstream data Advantages lower cost: without seed Residue downstream pattern Coupler RSOA Upstream data Disadvantages Erase of downstream pattern is a challenge if downstream uses intensity modulation Upstream Eyediagram Alternative modulation formats (DPSK, SCM & IRZ) used to facilitate the erasure of D/S pattern HUAWEI TECHNOLOGIES CO., LTD. Page 15

16 Comparison of Colorless Lightsources Scheme Spectrum slicing: LED Spectrum slicing: SLED/SOA Injection locked FP with ASE injection Injection locked FP with laser injection Injection locked FP with self-seeding RSOA: with ASE injection RSOA: laser array seeding Bit rate/channel Low, <155 Mb/s No. channels Low, 16 Low, <155 Mb/s Medium, ~32 Pros Very cheap No seed needed Inexpensive No seed needed Low, ~1.25Gb/s Medium, ~32 Inexpensive Medium, >2.5Gb/s Medium, ~32 Inexpensive Medium, >1.25Gb/s Medium, ~32 Inexpensive No seed needed Medium, <5 Gbit/s Medium, ~32 Relatively high bit rate Medium, <5 Gbit/s High, >32 Relatively high bit rate Cons Poor scalability and reach Low bit rate and short reach Non-standard FP needed (wide gain spectrum) RIN limits bit rate and transmission distance Non-standard FP needed (wide gain spectrum) Polarization dependent upon injection Non-standard FP needed (wide gain spectrum) Polarization dependent upon injection Relatively expensive, Seed source needed Chromatic dispersion limited Laser bank seed source needed Polarization dependent, backscattering problem RSOA with remodulation Medium, <5 Gbit/s High, >32 Relatively high bit rate No seed source Downstream extinction ratio is limited Backscattering affects upstream performance REAM High, >10 Gbit/s Low, <32 High bit rate Tuneable laser High, 10Gbit/s High, 32 Good output power => long reach No seed needed Wavelength flexible Expensive; Relatively high injection power Backscatter affects upstream performance Expensive External modulator needed Wavelength assignment algorithm needed HUAWEI TECHNOLOGIES CO., LTD. Page 16

17 目录 WDM PON Overview WDM PON Technologies System Performance Limitations Summary and Discussions HUAWEI TECHNOLOGIES CO., LTD. Page 17

18 System Impairments Fiber Loss Fiber dispersion Intensity noise from BLS Rayleigh backscattering Backscattering of BLS seed Backscattering of upstream and downstream signals Noise from colorless ONUs ASE noise from RSOAs Intensity noise and mode partition noise from IL FP lasers Reflection in the fiber link Not an intrinsic issue; can be minimized with proper installation of ODN HUAWEI TECHNOLOGIES CO., LTD. Page 18

19 RSOAs with BLS Seeding System Impairments Fiber dispersion Rayleigh backscattering and ASE noise Transmission Limits Dispersion limit D Lσ 0.25T For 100GHz channel spacing, L 30 km OSNR limit OSNR = = P 1 2 RIN rp + P seed ASE Ge + P 2αL P Rx _ sig seed _ scattering α P sig _ scattering 1 2 G P hνf GB e n 0 αl seed α OSNR e 2αL α + SP min 2 seed GP seed e 2αL α SG / 2 1 SG / 2 Rayleigh scattering coefficient S = C(1 e 2αL ) α S 2α HUAWEI TECHNOLOGIES CO., LTD. Page 19

20 RSOAs with BLS Seeding OSNR vs. Fiber Length OSNR vs. RSOA Gain RSOA gain G = 15 db G = 20 db G = 25 db Optimized Gain Fiber Length 20 km 30 km 40 km OSNR (db) OSNR (db) Dispersion limit for 100 GHz channel spacing Fiber Length (km) RSOA Gain (db) System design implication: RSOA gain needs to be optimized for different fiber length HUAWEI TECHNOLOGIES CO., LTD. Page 20

21 IL FP Lasers with BLS Seeding System Impairments Fiber dispersion: not a big issue at 1.25Gb/s The linewidth of well-locked FP laser is less than 0.1nm Rayleigh scattering and ASE noise Transmission Limits OSNR Limit OSNR = 1 4 rp seed Ge 2αL α 2 + N FP P ( P sig seed e ) e 2αL αl α α + SP seed + P sig e αl SGm / 2 1 SG / 2 m OSNR min Rayleigh scattering coefficient RIN from FP laser S = C(1 e 2αL HUAWEI TECHNOLOGIES CO., LTD. Page 21 S N ) α S 2α 2 = Ωdω πσ FP ( ω) kcn phpseed H ( ω) [( ω ϖ ) + Ω ] FP ( Pseed ) S FP( ) = ω dω

22 IL FP Lasers with ASE Seeding Seed Power 0 dbm 3 dbm 6 dbm IL FP Power 0 dbm 3 dbm 6 dbm OSNR (db) OSNR (db) Fiber Length (km) Fiber Length (km) System design implications Once IL FP laser is in well-locked condition, higher seed power results in worse performance due to ASE noise and backscattering. Higher output power from IL FP laser leads to better performance need higher bias current. When FP laser operates with higher bias current, more optical injection power is needed. HUAWEI TECHNOLOGIES CO., LTD. Page 22

23 IL FP Lasers with ASE Seeding Front Facet Reflectivity R1 = 0.01 R1 = 0.03 R1 = Fiber Length 20 km OSNR (db) OSNR (db) Fiber Length 30 km Fiber Length 40 km System Design Implications Fiber Length (km) Front Facet Reflectivity Higher front facet reflectivity leads to better performance Higher front facet reflectivity stronger filtering of intensity noise from seed light Higher front facet reflectivity Lower gain lower Rayleigh scattering for upstream However, front facet reflectivity has to be kept small FP laser gain spectrum broadening wider operating wavelength range more channels HUAWEI TECHNOLOGIES CO., LTD. Page 23

24 Tunable Lasers System Impairments Fiber dispersion is not an issue at 1.25Gb/s Fiber loss is the limiting factor Transmission Limits Loss budget P sig e αl 2 α P rec 1 2 i.e. L ln( P sig α P ) Transmission distance is limited by Tx power and Rx sensitivity Tx power: 0 dbm, Rx sensitivity: -30 dbm, Fiber Loss: 0.3 db/km Transmission distance: 100 km α rec HUAWEI TECHNOLOGIES CO., LTD. Page 24

25 目录 WDM PON Overview WDM PON Technologies System Performance Limitations Summary and Discussions HUAWEI TECHNOLOGIES CO., LTD. Page 25

26 Conclusions WDM PONs are attractive due to Logical P2P connection, guaranteed bandwdith Protocol and data rate transparency, better security However, significant cost reduction of WDM PONs is needed! Key challenges for WDM PONs: Colorless ONUs RSOAs and IL FP lasers is less expensive, but performance need improvement Tunable laser has better performance but cost is a big issue System Impairments in WDM PONs are reviewed Fiber loss and dispersion ASE noise and Rayleigh backscattering Design trade-off for seeded WDM PONs RSOA with BLS seed RSOA gain needs to be optimized for different fiber length IL FP laser with BLS seed BLS power need to be optimized to achieve the best OSNR Front facet needs to be optimized for OSNR and operating wavelength range HUAWEI TECHNOLOGIES CO., LTD. Page 26

27 Thank you HUAWEI TECHNOLOGIES CO., LTD. Page 27

Joint ITU-T/IEEE Workshop on Next Generation Optical Access Systems. Requirements for Next Generation PON

Joint ITU-T/IEEE Workshop on Next Generation Optical Access Systems Requirements for Next Generation PON Junichi Kani 1 and Russell Davey 2 1 NTT Access Network Service Systems Labs, NTT 2 BT Outline Introduction