coherent pluggable modules for 100g and 200g

1 © 2014 Oclaro, Inc.© 2014 Oclaro, Inc.

Indium phosphide enabled coherent pluggable modules for 100G and 200GOFC 2014 – Market Watch 100/400G Pluggable Optics and its Enabling Technologies

March 13, [email protected]

2 © 2014 Oclaro, Inc.

Market Evolution

• The 100G marketcan be consideredin two subgroupsprimarily dictated bythe DSP strategy

• Both analog & digitalmarkets are largeand will transitiontowards pluggables,especially for metroapplications

• New market dynamic coming into play with carriers pushing for interoperability

MSA‐168(Transponder)MSA‐168(Transponder)

Discrete(Gold Boxes)Discrete(Gold Boxes)

CFP2(Analog)CFP2(Analog)

CFP(Digital)CFP(Digital)

DSP is part of moduleDSP is part of module

DSP is on line-cardDSP is on line-card

Group 1: “Analog” Discrete → CFP2

Group 2: “Digital” MSA‐168 → CFP


100G/200G Coherent DetectionMarket Perspective

Customer secures & controls DSPCustomer secures & controls DSP Module vendor secures & controls DSPModule vendor secures & controls DSP

Discrete(Gold Boxes)Discrete(Gold Boxes)

CFP2(Analog)CFP2(Analog)

CFP(Digital)CFP(Digital)

MSA‐168(Transponder)MSA‐168(Transponder)

Volume estimates are based on Oclaro analysis and 3rd party

estimates. Split is likely to vary, but at the component level the ratios

are not too important.

Volume estimates are based on Oclaro analysis and 3rd party

estimates. Split is likely to vary, but at the component level the ratios

are not too important.

Annual volumes


10G Footprint Evolution

OC-192 TOA

Tunable Tx Assembly

Tunable-XFPTunable SFP+ TOSA

Tunable-CMZ

Coaxial Interconnect

T-SFP+ TOSA has TOA functionality & wavelength tunability & control!


Trio of InP Building Blocks for 100G

Single material system delivering high performance, increased density and reduced power dissipation Single material system delivering high performance, increased density and reduced power dissipation

Mach Zehnder Modulators Tunable Lasers Coherent Receivers

Trio of InP based building blocks enabling next generation of photonic components for coherent applications


Packaged NLW laser, dual QPSK MZ and polarisation multiplexer with LO output

2nd generation transmitter designed for CFP2– RF on rear of package; DC on long side of package– Dual fiber feed through

1st Generation Based on 40G DQPSK package


Transmitter results (32Gbaud)

• Results are essentially identical to LiNbO3– Consistent with customer results

• For 16-QAM, see paper by Cisco Optical GmbH team– T. Duthel, P. Hermann, T. Winkler von Mohrenfels, J.E. Whiteaway, T. Kupfer,

“Challenges with Pluggable Optical Modules for Coherent Optical Communication Systems”, W3K.2, OFC 2014

Back‐to‐back 35,500 ps/nm CD


100G Micro InP Coherent Receiver

• Single polarization 100G InP chip size 1.2x3.33mm comprising monolithic 90deg hybrid mixer, 4 matched integrated waveguide photodetectors and 4 on-chip capacitors

• Packaged with Signal X&Y polarization split to 2 orthogonal polarization InP chips• LO split into InP chip enabling mixing with each Signal polarization within hybrid 90.• 4 differential input TIA with AGC to 4 differential RF outputs XI,XQ,YI,YQ• Multi-layer fully ceramic package technology with GSSG transmission line optimised for low RF loss• Designed for cost sensitive metro or long haul applications• Miniaturised package size 5x12x25mm for CFP2 modules

XI

XQ

YI

YQ

LO

Signal

Beam split

Pol

Split

Rotate

90°HybridMixer

90°HybridMixerVOA

MPD

X‐Pol

Y‐Pol

InP Chip

Mechanically compliant to Micro ICR OIF IA proposal, OIF‐DPC‐MRX‐01.0 for CFP2 Modules


100G Coherent Receiver Evolution• InP PIC miniaturization

– 60% smaller PIC than current generation

• Reduced E&O complexity• Improved response,

bandwidth & CMRR• Temperature & wavelength

flattened• Includes VOA & power

monitoring

1st Generation For 5”x7” MSA

2nd GenerationFor “CFP2”


Coherent CFP2

CFP2: 107.5 x 41.5 x 12.4 mm3 = 55 cm3

iPhone 5S: 123.8 x 58.6 x 7.6 mm3 = 55 cm3

https://www.apple.com/iphone‐5s/specs/


CFP2

DSP

RF design

• Need to consider entire RF link from DSP to PIC

• Key challenges– CFP2 connector– Tx/Rx package

DAC InPMZM

CFP2connector Driver Tx

PackageHostPCB

ADC InPPD

CFP2connector TIAHost

PCBRx

Package


Pre-emphasis and driver choices• DSP designs include pre-emphasis capability

– New designs have higher resolution and are able to compensate for ripple in amplitude response

• For limiting designs can compensate for RF loss to driver– Host board loss and additional loss due to pluggable interface can be

compensated for • For linear designs can compensate for RF loss from DSP through

to modulator– Can therefore handle lower modulator bandwidth compared to limiting

QPSK

• Graph shows transmitter with test board loss included

• Very linear response up to 30GHz– Linear roll-off can be

compensated for in pre-emphasis


RF path from CFP2 connector through to driver• Green is simulated S21 from CFP2 connector to driver• Red is CFP2 connector loss

– Loss at 20GHz <1dB but features at lower frequencies might require additional compensation


RF design• Achieving small form factors at lower cost points requires co-planar RF

interconnect solutions– Replace GPPO connector/cables by leaded co-planar interface

• Realistic loss through package wall and interconnecting ceramic tile to Mach Zehnder is 1 to 1.5dB– Packaged bandwidth would be less than 20GHz even for 40GHz

modulator bandwidth• Design of transmitter gold box package necessarily focused on

minimizing path length induced material loss and managing transitions to achieve linear roll off


DSPs allow for performance trade-off’s100G DSP simulations

• Oclaro simulations, CLiSST V1.7– InP MZ transfer function– < 0.5dB penalty 25 15 GHz

• Oclaro simulations, NEL DSP– Conventional components– < 0.5dB penalty 25 15 GHz

ClariPhy LH DSP EmulatorClariPhy LH DSP Emulator NEL LH DSP EmulatorNEL LH DSP Emulator

128 Gb/s, Tx Electrical b/w 10‐21 GHz, Rx Electrical b/w 18 GHz, 500 MHz laser linewidth3, 4 or 5 pole Butterworth filter at Tx, 4 Pole Butterworth at Rx, 0.3nm order 3.4 Gaussian optical filter

Combined Tx & Rx Variations

0). Optical BW 30 GHz =; 1). Prec = ‐10 dBm; 2). NTT BER (7/2012 results)

Additional features to ease the photonic challenge are likely to become available!


Laser phase noise for narrow linewidth laser• Typical Lorentzian linewidth 200-250kHz • Frequency noise spectrum is just as important

– Optimized laser design, local carrier filtering and drive circuit to reduce electrically induced noise

• New DS-DBR designs show only fraction of a dB penalty compared with instrument-grade reference lasers

• Some increase in FM noise at low frequencies due to shot noise in tuning sections– Since electrically tunable, current fluctuations translate to optical FM

fluctuation• Challenge in small form factors is to achieve desired low noise

drive of laser– Key area of work for design both of gold box and surrounding

electronics/interconnect


CFP2 power dissipation• Main contributors

– Laser including TEC– Modulator drivers– Mach-Zehnder including TEC– Coherent receiver

• Modulator contribution– Need to be <5Vpp driver swing to achieve

<1W/channel• Most efficient driver technology is differential

in/ differential out, 2 stages and InP material– Single-ended has higher power requirements– Alternative driver materials are SiGe or GaAs

• Modulator material uses AlQ InP to support 2Vπ of <5Vpp

• TEC dissipation for laser and MZ– AlQ enables higher temperature operation

Laser with TEC, 30%

Modulator driver, 30%

Modulator with TEC, 20%

Receiver and misc, 15%

EOL, 5%

12W total


Driver and Mach-Zehnder optimization

• Modulator material uses AlQ InP to support 2Vπ of less than 5Vpp– Can go to deeper bias without incurring excess insertion loss– PQ InP would require 6Vpp

PQ Mach Zehnder contour plot AlQ Mach Zehnder contour plot


Choosing modulator driver: Voltage and Vπ trade-offs• The modulator driver output swing directly impacts the power dissipation

– Worked with driver manufacturers to define the best compromise between driver dissipation and the modulator Vπ

• At a basic level the modulator Vπ is a direct compromise with bandwidth – Modulator dissipation primarily

dependent on number of gain stages required, driver structure and output swing

• The best performance compromise can be achieved with DE/DE drivers and a MZ with a 2Vπ of less than 5Vpp


Conclusions• Next generation 100G/200G coherent pluggable

transceivers are in the sampling stage now• Significant progress has been made from photonic

integration in InP through packaging• New DSPs and driver technologies allow to manage

performance trade-off’s– Need to take a holistic approach to product design from optical

chip to module• Coherent CFP2 can be achieved with 12W power

dissipation and performance suitable for long-haul applications

coherent pluggable modules for 100g and 200g

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