Transcript Balanced receiver

Fiber Optic Network Design
Class 8
C. S. Yan, X. Wu, M. Y. Li
Dept. of Opt. Engr., ZJU
2013
Content
Introduction
Development of optical fiber communication
Bottlenecks
Basic theory of COC
Advantages, Principles, Structures and types
DPSK
DP-QPSK
Simulation of DPSK system by Optisystem
Pulse generation
Sequence decoder
Balanced receiver
Exercise today
Reference
Introduction
• Higher Spectral Efficiency
• Higher Data Rates
• Higher Receiving Sensitivity
Introduction
Development process on optical transmission rate and
transmission distance product for thirty years
bottlenecks
Revolution?
Moore's Law
Introduction
Development of optical fiber communication
in the earlier years
Year
1966
1976
1976
1976-1978
1983
1988
1989
Development
C. K. Kao: fiber as communication medium
Fiber loss <0.47dB/km (1.2um)
44.7Mb/s, 10km (Atlanta, multi-mode fiber)
34Mb/s (100Mb/s), 64km (Japan)
400Mb/s (1.6Gb/s), 3400km, (Japan’s
north-south route)
6400km, TAT-8 Atlantic submarine cable
13200km, TPC-3/HAW-4 Atlantic submarine
cable
Introduction
What is the bottlenecks for DWDM
1. Chromatic dispersion
2. polarization mode dispersion
Introduction
What is the bottlenecks for DWDM
3. Nonlinear effect
Nonlinear effect
Stimulated Raman
Scattering
Four-wave mixing
Cross
phase
modulation
Bottlenecks
SNR degradation as the number of
channel increases
Limit the channel spacing
Limit the number of channels
4. Electronic rate
When >30GHz，limited by electronic circuit and ADC chip
Introduction
How to break through the bottlenecks
——Optical Time Domain Multiplexing (OTDM)?
Electronic signals
Optical signals
4x
40Gb/s
delayed
S
1x 160Gb/s
8
Introduction
The advantages of OTDM
Characteristics Advantages
Single
wavelength
operation
All-optical
digital signal
processing
No gain flattening
Simple dispersion managing
Bandwidth on
demand
Flexibility to provide emergency service access
Achieved
through the
slot allocation
routing
Data format and protocol transparent transmission
Overcome the electronic bottleneck
Improve network capacity
Network signal stream all-optical regeneration
Reduces signal noise and crosstalk accumulation
Truly transparent transmission of optical signals
Introduction
The Disadvantages of OTDM
High price
Ultra-narrow optical pulse laser
Optical clock extraction and de-multiplexing
Severe nonlinear effects
Introduction
Combination of OTDM and WDM
4 x 40Gb/s
160Gb/s
WDM multiplexer
of Add-Drop
160Gb/s
OTDM add-drop
4 x 40Gb/s
40Gb/s 40Gb/s
160Gb/s
4 x 40Gb/s
160Gb/s
WDM demultiplexer
of Add-Drop
160Gb/s
OTDM demultiplexer
4 x 40Gb/s
OTDM multiplexers
160Gb/s
160Gb/s regenerated
Basic theory of coherent optical communication
How to breakthrough?
COC?
Amplitude
Modulation
WDM
OTDM
Phase
Frequency
Polarization
Modulation
Coherent
Optical
Communication
Basic theory of coherent optical communication
Opportunities come again COC
2004, M. G.
Taylor, PTL,
Proposed to
restore the signal
using DSP, Digital
coherent receiver
technology
2004, 20Gbit/s,
QPSK system
solve the problem of channel attenuation
But hard to large scale Commercial
Replaced by EDFA in the 1990s
2002, R. A. Griffin (UK), DQPSK
Basic theory of coherent optical communication
Advantages of COC
Advantages
High sensitivity and long Sufficiently close to the quantum limit
by raising the power of the LO light.
distance relay
Good wavelength selectivity
and large communication
capacity
linear system, The linear distortion
Large dispersion and
owing to dispersion and PMD can be
nonlinear toleration
completely compensated.
Low
cost,
high
reliability,
Use DSP to restore the data
Commercialization,
Use electronic devices for
Dispersion compensation and
Polarization equalization
Support various modulation M-PSK, M-QAM , OFDM, with higher
spectral efficiency
schemes
Basic theory of coherent optical communication
The principle of COC
E s (t )  E s exp[  j ( S t   S )]
EL (t )  EL exp[  j (Lt   L )]
Basic theory of coherent optical communication
The principle of COC
Detector Responsivity
I  R( PS  PL )  2 R PS PL cos( IF t   S   L )
Optical power
Because PL  Ps ,
R( PS  PL ) can be filtered as a DC term
 Homodyne detection :
I ( t )  2 R Ps PL cos( S   L )

 Heterodyne detection : I ( t )  2 R Ps PL cos( IF t   s   L )
Basic theory of coherent optical communication
The principle of COC
Homodyne
detection
Advantages:
Heterodyne
detection
I out  PL
Optical
phase SNR is two times
lower
than
High
frequency locked loop (PLL)
homodyne
stability
Narrow bandwidth
 s   L  0 or C
Frequency tunable
Disadvantages:
Basic theory of coherent optical communication
Structures and types of coherent receivers

 DPSK 

  RZ

 Based on phase modulation  QPSK   NRZ

 (Differential phase shift keying) 
DP
QPSK



8QAM

Cohenent 


Based
on
QAM
(phase
&
amplitude)

16QAM
Receiver 
64QAM
(Quadrature Amplitude Modulation)



Optical frequency division multiplexi ng  OFDM



Basic theory of coherent optical communication
Signal Modulation of Differential phase
shift keying (DPSK)
 phase change between 0 and 1 code
Basic theory of coherent optical communication
Coherent demodulation process of DPSK
Basic theory of coherent optical communication
Modulation formats comparison of
coherent receivers
100Gbit/s
50GHz channel spacing
OSNR=0.2dB
Basic theory of coherent optical communication
Modulation formats comparison of
coherent receivers
After 1600km
transmission
in standard
single-mode
fiber
Dispersion can
be compensated
by DSP. For the
same dispersion,
it has different
requirement for
the computing
power of the
DSP (serials)
Basic theory of coherent optical communication
Coherent receiver of Dual-polarization
quadrature phase shift keying (DP-QPSK)
Polarization
separation
Demodulation
Phase  intensity
Balanced receiver
TIA: Trans-impedance amplifier
Optical  Electrical
Basic theory of coherent optical communication
90 phase shift mixer of DP-QPSK
Optical fiber type
Free space type
Basic theory of coherent optical communication
90 phase shift mixer of DP-QPSK
LiNbO3 waveguide type
Si-based monolithic integration
Bell Lab 2010
Basic theory of coherent optical communication
90 phase shift mixer of DP-QPSK
Si-based monolithic integration type
Furukawa
InP-based monolithic integration type
Bell Lab 2011
Basic theory of coherent optical communication
90 phase shift mixer of DP-QPSK
Major international manufacturers of 100Gbit / s coherent receiver
Basic theory of coherent optical communication
90 phase shift mixer of DP-QPSK
Physical map of InP based monolithically
integrated coherent receiver by HHI and U2T
Simulation of DPSK system by Optisystem software
DPSK—pulse generation
 2
i  1    , i  1,2, M
M

ki  k 1  
M  2n
I ki  cos ki , i  1,2, M
Qki  sin  ki , i  1,2, M
Constellation
diagram
Simulation of DPSK system by Optisystem software
M-ARY pulse generator and
Threshold detector
input M-ary signal
pulse position
linear gain
parameter Bias
bit period
duty cycle
if the signal input has a value
of -3.3, the output level will be
-3, since -3.3 is between -3.5
and -1.5.
Simulation of DPSK system by Optisystem software
DPSK—pulse generation and decoding
Simulation of DPSK system by Optisystem software
DPSK sequence decoder
 Qk
  arctan
 Ik
 2
i  1    , i  1,2, M
M

ki  k 1  
M  2n
I ki  cos ki , i  1,2, M
Qki  sin  ki , i  1,2, M
i



 k   k 1   M  1
2
The DPSK decoder will
calculate the value of i from
the phase difference between
consecutive signals k and k-1:
Simulation of DPSK system by Optisystem software
DPSK sequence decoder
Assuming ϕ=0, if bits
per symbol (n) equals 2,
and M=4, then the
values for I and Q will
be:
Assuming ϕ=0, if bits
per symbol (n) equals
3, and M=8, then the
values for I and Q will
be:
Simulation of DPSK system by Optisystem software
Balanced receiver
Simulation of DPSK system by Optisystem software
Balanced receiver
I 
1
R Ps  PLO   R Ps PLO cos IF t   IF 
2
Eliminate intensity
noise, improve
sensitivity
1
I   R Ps  PLO   R Ps PLO cos IF t   IF 
2
I  2 R Ps PLO cos IF t   IF 
Exercise today
Set up and study
the system
Reference
刘卫华. 用于100Gbit/s 相干通信的90°相移光混合器研究. 华中科
技大学博士学位论文. 2012
王甲琛. 基于FPGA的DPSK调制解调技术的设计与实现. 西安电子科技
大学硕士学位论文. 2010