4th Symposium on Optical Interconnect for Data Centres VCSEL-based solderable optical modules Hideyuki Nasu FITEL Products Division Furukawa Electric Co., Ltd. H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres
Contents Solderable optical modules for the front panel connection Simple and low-cost on-board optics assembly with polymer-waveguide embedded PCB >1.3 Tb/s on-board optical module Summary H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 2
Front panel applications using SFFs 12-channel optical modules 14-Gb/s 12-channel TX/RX 28-Gb/s x 4-channel duplex Temperature profile Plastic microlens Sn-Bi solder reflow-capable Maximum temperature: 190 C QSFP+/QSFP28 CXP QSFP28 MPO-type transceiver 4-channel optical modules 14-Gbit/s x 4-channel TX/RX 28-Gbit/s x 4-channel TX/RX Temperature profile 13.0mm 14.7mm 3.4mm QSFP+/QSFP28 Sn-Ag-Cu solder reflow-capable MiniSAS Maximum temperature: 250 C SFP28 QSFP28 MPO-type transceiver MT (8.0mm 7.0mm) H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 6.5mm 10.7mm 1.5mm 4th Symposium on Optical Interconnect for Data Centres 3
QSFP28 SR solution Eye diagrams TX output (Optical) Loop-back test Operated at 28.05 Gb/s PRBS 2 31-1 Housing temperature: 71 C Ch1 Ch2 Ch3 Ch4 RX output (Eelctrical) BER bathtub curves Housing temperature: 31 C Housing temperature: 55 C Housing temperature: 71 C H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 4
SM VCSEL-based optical modules Single mode 1300-nm 10-Gb/s x 4-channel engine for LR4 Driving conditions Vcc = 3.3 V Bias Current = 11 ma Modulation current = 10mA Ta = 25degC Input signal : 10.3125Gbps / PRBS_2 31-1 / Vamp_diff = 900mV Ch1 Ch2 Ch3 Ch4 B to B Pf = -2.7 dbm Pf = -2.7 dbm Pf = -2.1 dbm Pf = -2.7 dbm SM 10km Pf = -6.3 dbm Pf = -6.5 dbm Pf = -5.8 dbm Pf = -6.8 dbm H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 5
SM VCSEL-based optical modules BER characteristics Back to Back 10km Transmission This approach keeps the sample packaging platform for both MM and SM optical modules H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 6
Long distance MMF transmission at 25.78 Gb/s 1060-nm VCSEL-based link OM4-like MMF for 1060 nm. Encircled flux back-to-back 100m 300m 500m 700m 1000m Low bias current operation (3mA) Calculated fiber bandwidth Error free at 1 km K. Nagashima, T. Kise, Y. Ishikawa, and H. Nasu, A Record 1-km MMF NRZ 25.78-Gb/s error free link using the 1060-nm DIC VCSEL, IEEE Photon. Tech. Lett., vol. 28 no. 4, pp. 418-420, Feb. 2016. H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 7
High-density on-board optics On-board optics is a promising solution for high-density optical interconnects How do we mount on-board optics? Short electrical transmission lines to suppress degradation of high data rate signals. Clinchers Heatsink (lid) Complicated board assembly Parallel-optical module Electrical pluggable socket Optical connector Costly process Complex 3-D optical wiring Disturb air flow Optical modules Airflow LSI H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 8 PCB
What is available with polymer-waveguides? Polymer waveguide-embedded PCB Simple and smart optical wirings 3-D optical wirings inside a PCB Simpler assembly Better airflow Flexible design for optical wiring T. Ishigure, JIEP-OPT (2013) H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 9
Proposal for high-density board assembly Simple optical and electrical interfaces on polymer waveguide embedded PCB Reducing piece parts LOW COST Reducing assembly cost HIGH DENSITY Minimizing footprint Solderable module Screwed Heatsink / cover Sn-Ag-Cu solder-reflow Optical connector Optical fiber POM Screwed PCB LSI Solder reflow PWG POM PCB Solder reflow LSI Electrical socket PCB : Printed circuit board LSI : Large scale IC Solder bump No electrical and optical connectors Electrical and optical interfaces on the bottom surface H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 10
Optical coupling interface No need an optical connector, but a mechanical motion induced by a self-alignment effect of melted solder is concerned. VCSEL/PD Lens array PWG core Lens array 50 mm mechanical motion lens VCSEL/PD PCB Optical PCB Technical challenges POM Solder bumps Solder LGA bump A single lens coupling system + Optical axis stabilization during the solder reflow Coupling structure with two collimator lens arrays Wide optical axis displacement tolerance complexity and higher cost A single lens array system Reducing piece parts Reducing assembly complexity and cost H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 11
Concept of optical module mounting Schematic view Guide-hole Inner electrical wiring Optical module Lens-array Front view VCSEL/PD array Glass epoxy substrate Solder bump LGA PCB Stud-pin Mirror Polymer waveguide Electrical connection Optical connection Side view Optical connection Electrical connection H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 12
Fabrication of 12-channel modules Illustrations and photographs 14-Gb/s x 12-channel (TX/RX) 12-Ch VCSEL/PD 12-Ch VD/TIA LGA 25-Gb/s x 4-channel transceiver module 4-Ch PD 4-Ch VCSEL 4-Ch TIA 4-Ch VD LGA Top surface Bottom surface Dustproof cover Microlens array Guide holes LGA H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 13
Optical module mounting to Optical PCB Schematic illustration for module mounting 12-channel optical module Top surface: Thermal dissipation The whole area of top surface can be used for thermal dissipation Polymer-waveguide PCB Bottom surface: Electrical interface (land grid array) Optical interface H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 14
Optical axis displacement of lens array Measurement of axis displacement Guide hole Δy Guide hole Lens (ch12) Lens (ch1) Δx Δx Δy y Sample size: TX 6 pcs, RX 5 pcs Channel 12 Channel 1 X Dy [mm] Dy [mm] Axis displacement < 5mm ±5mm ±5mm ±5mm Dx [mm] ±5mm Dx [mm] H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 15
Polymer waveguide-embedded PCB Parallel-optical module Differential transmission line V-groove with mirror LGA Y X Plastic stud-pin Measured displacement: Dx,Dy < 3 mm Material Process Propagation loss Optical PCB Polymer waveguide Summary of PWG characteristics Epoxy Photolithography 0.17 db/cm (1060 nm) Refractive index in core/clad 1.581/1.541 Type of refractive index profile Step index Total displacement: 8 mm < 12 mm (Module: 5 mm, PWG: 3 mm) Shape of core Length Core pitch Square (35 mm 35 mm) 42.45 mm 250 mm Numerical aperture 0.3 Optical bandwidth 6.6 MHz km H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 16
Assembly process Optical PCB H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 17
Assembly process Masking for the optical interface Masking tape H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 18
Assembly process SMT and solder-reflow process Solder-reflow Mini-SMP connectors Optical module Dustproof cover In compliant with JEDEC level 3 The peak temperature is 235ºC H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 19
Assembly process Removing the dustproof cover H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 20
Assembly process Removing the masking tape H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 21
Assembly process Dust cap and heatsink attachment Heatsink Dust cap H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 22
Assembly process Edge connector attachment Edge connector H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 23
Assembly process Fiber cable connection Ribbonized fiber H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 24
14.0-Gb/s x 12-channel modules Optical coupling loss Maximum coupling losses : TX : 3.4 db @ Ch2 RX : 2.4 db @ Ch1 The worst total coupling loss < 6 db Eye diagrams TX output (optical) CH1 CH2 CH3 CH4 CH5 CH6 RX output (electrical) CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 CH9 CH10 CH11 CH12 CH7 CH8 CH9 CH10 CH11 CH12 Clearly opened eye diagrams for all channel at both TX and RX H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 25
14.0-Gb/s x 12-channel modules BER characteristics Link transmission: 14.0 Gb/s, NRZ PRBS 2 31-1 BER bathtub curves Jitter margin Error-free transmission achieved Averaged minimum sensitivity : -10 dbm Averaged jitter margin : 0.3 U.I. (including test environment) H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 26
25.78-Gb/s x 4-channel transceiver Eye diagrams and BER characteristic Loop back test without CDR TX output CH1 CH2 CH3 CH4 RX output CH1 CH2 CH3 CH4 H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 27
>1.3 Tb/s on-board optical module 28-Gb/s x 24-channel optical transceiver module Top view Bottom view Thermal dissipation Data rate density: Optical module 1344 Gb/s/inch 2 (2.08 Gb/s/mm 2 ) 10-cent coin Optical interface Electrical interface Power density: 13.5 mw/channel/gb/s Integrated CDR in TX and RX Bundled RF connector Test system Copper plains Heat dissipation Copper filled vias Optical module Guide frame LGA interposer Organic substrate VCSEL/PD VD/TIA Plastic microlens Structure of optical module (cross section) H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 28
>1.3 Tb/s optical module Loop-back link performance Eye diagrams TX 28.05 Gb/s, PRBS 231-1 Ch1 Ch7 Ch13 Ch19 Ch2 Ch8 Ch14 Ch20 Ch3 Ch9 Ch15 Ch4 Ch10 Ch5 Ch6 BER bathtub curves Ch1 Ch7 Ch13 Ch19 Ch2 Ch8 Ch14 Ch20 Ch21 Ch3 Ch9 Ch15 Ch21 Ch16 Ch22 Ch4 Ch10 Ch16 Ch22 Ch11 Ch17 Ch23 Ch5 Ch11 Ch17 Ch23 Ch12 Ch18 Ch24 Ch6 Ch12 RX Ch18 Ch24 Jitter margin: 0.35 U.I. (w/o CDR) 0.45 U.I. (w/ CDR) H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 29
Summary VCSEL-based solderable optical modules were developed for the Front Panel Optics and On-Board Optics. QSFP+ CXP QSFP28 SM VCSEL solution for a longer reach applications Simple and low-cost on-board optics assembly with polymerwaveguide embedded PCB was introduced. 14-Gb/s x 12-channel TX/RX 25-Gb/s x 4-channel transceiver >1.3 Tb/s on-board optical engine for high-density optical interconnects H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 30
Thank you! H. Nasu/ FITEL Products Division, Furukawa Electric Co., Ltd. 4th Symposium on Optical Interconnect for Data Centres 31