Transcript 2011 Study Plan

A 10 Gb/s Photonic Modulator and
WDM MUX/DEMUX Integrated with
Electronics in 0.13um SOI CMOS
High Speed Circuits & Systems Laboratory
Joungwook Moon
2011. 5.25
Contents
1.
Introduction
2.
Implementation
3.
Conclusion
Introduction
• Author :Andrew Huang. Luxtera, Carlsbad, CA
(ISSCC 2006)
• Manufacturable yield-frendly photonics components
combined with electronics using a 0.13um SOI
process for PowerPC processors
• A 10Gb/s optical modulator integrated with a driver
and 4-channel WDM MUX/DEMUX w/ integrated
tuning circuits
– WDM MUX/DEMUX(Wavelength division multiplexing) : To
increase capacity and speed of commucation, different kind
of data put into a single fiber. An optical fiber can carry
maximum 80 wavelength of data.
Implementation - Waveguide
• C-band (1.5um) optical waveguides are formed
by a high reflective index core of transparent
silicon & low reflective index index silicon dioxide
Wavelength Band
Waveguide structure & Optical profile
@ Ref.[2]
• C-band (conventional wavelength band) :1530nm ~ 1565nm
Holographic Lens
• Holographic lens(HL) couples light normal to the
surface of the die with < 1.5dB loss
• HL allows inexpensive
10um fiber core
wafer scale testability
(Good replacement for the refract-
-ing lens in maching application)
waveguides
Holographic
lens
SEM photograph of a holographc lens
Modulator (1)
• Modulator uses a free-carrier-effect-based device
in a Mach-Zender interferometer
- Light is split evenly into two arms.
- The light is phase-modulated.
- Differential accumulation of phase (ΔΦ) causes
the recombined light to interefer.
P= 0.5 + cos(∏/2 + ΔΦ)/2
• A reverse-biased lateral
PIN diode
(contrast to conventional method
based on diffusion/recombination)
• The speed of the resulting
device is limited by RLC
Schematic diagram of a phase
modulator in one arm of the MZI
Modulator (2)
• In a lumped configuration, junction length needed for
sufficient phase shift would be parastic-limited to
< 10Gb/s
 To overcome this lumped-RC speed limit is to design a
travelingwave electrode. (designed as a part of the
microwave transmission line)
• On chip terminations are integrated at the end of the
microwave transmission lines to supperss backrelfections
• The characteristic impedance of the transmission line
+ PN diode : Total system impedance = 25Ω
• The modulator has a length of 2mm, microwave loss
would be sufficiently small
Integrated Driver
• A cascoded thin-gate-oxide transister swich is used
• Pre-driver chain drives the switch transistor
• Cascode device is used to shield the high-performance
switch from the relatively high voltages required by
the modulator elements
• The active area for the modulator
driver is 0.08mm2
• Total area is 2.6mm2 including 2mm
modulator, termination network,
and pads
Integrated driver connected to
one MZI arm
CMOS optical modulator with Differential Driver
Integrated Driver
• A cascoded thin-gate-oxide transister swich is used
• Pre-driver chain drivesthe switch transistor
• Cascode device is used to shield the high-performance
switch from the relatively high voltages required by
the modulator elements
• The integrated circuit yields
a 10-12 BER with a 223-1 PRBS
at 10Gb/s.
• Performance of the optical
modulator is entirely limited by
the driver
Optical eye of integrated modulator
plus driver at 10Gb/s
4-Channel DWDM AWG (1)
• A Key Advantage of integrated electronics and photonics
on a single chip is to raise yield of an optical device by
electronic control ciucuitry
• Optical 4-channel DWDM AWG with an 8b DAC array is
integrated (< 0.6mm2)
• DWDM: Dense Wavelength
Division Multiplexing
• AWG:
Arrayed waveguide grating
 generate a desired spectral function
Die shot of DAC array plus AWG element
4-Channel DWDM AWG (2)
• Forward-biased PIN junction phase Modulators
integrated into each arm of the AWG.
 offer great phase efficiency (90°/mA for 100um arm)
but lower speed & higher loss
• Each modulator is driven by an 8b 5/3 segmented DAC
to restore phase relationship (inducing random delay)
• After tuning, the crosstalk suppression is improved
by over 16db
Luxtera CMOS Photonic Tech.
from Luxtera (www.luxtera.com)
Conclusion
• Abstract
– Motolithic integration of both photonic and
electronic components operating at 10Gb/s
in a 0.13um SOI CMOS process
– A modulator uses free carrier plasma
dispersion in a reverse-biased PIN optical
phase shifer in a Mach-Zender
interferometer.
– An AWG demultiplexer uses a forwardbiased PIN phase shifter to compensate the
optical path length improving the channel
separation