muse xl-pon: general concept and approaches for burst-mode receivers emilio hugues salas university...

MUSE XL-PON: General Concept and Approaches for Burst-Mode Receivers

Emilio Hugues SalasUniversity of Essex

BB Cluster Meeting – 20th March 2007

1. Introduction (PON)2. XL-PON

Objective and technologies (overview) Characteristics Usage of Optical Amplifiers XL-PON Architecture

3. Burst Mode Receivers Previous AC/DC Coupling Techniques Edge Detection Technique

1. Simulation Results2. Experimental Results (Clock Recovery)

4. Conclusions

Overview


Passive optical network (PON)

downstream

#1

#N

ONToptical splitter

OLT

common fiber for both directions

upstream

„Triple play“ = Data, VoIP and Video on the same fiber


PON technologies: overview

Type Format Max. Data rate Split reach Budget

BPON ATM 0.6 GBps up, 1.2 GBps down 1:64 20 km

(G)EPON Ethernet 1.2 GBps up & down 1:16 20 km

GPON G.984.3 2.5 GBps down 1.2Gbps up 1:64 20 km B+ : 28dB

Standarisation:FSAN/ITU-T: NG-PON 10G/2.5G then 10G/10G, ~2010IEEE: 10G/1G then 10G/10G, target ~ 10km, 16 user


Objective of XL-PON:Reduction of network elements

BRAS

OLT

OLT

OLT

OLT

OLT OLT


XL-PON Characteristics

• Aims:

• increase the reach towards up to 100km

• increase the number of clients (splitting factor)

• The idea:

• utilize mature technology

• reuse & adapt proven TDM-based GPON technology

• reuse from long-haul network

• increase the data rate to 10Gbit/s

• In order to:

• >20Mbit/s average data rates even for 100‘s of users

• minimize system cost due to long-reach


XL-PON Characteristics: Power budget situation

Attenuation in an XL-PON:

Splitter: 35dB at 1:1024

Fiber: 0,25 dB / km 25dB at 100km

Total: 60dB

Power budget by transmitter and receiver at 10Gbit/s: < 20dB

Up to 40dB of amplification required!


Usage of optical amplifiers

• Available types of amplifiers

• fiber amplifiers C-band and L-band EDFA

• SOA (semiconductor optical amplifiers)

• others (Raman, non-linear mixing, ...)

#1

#N

ONToptical splitter

OLT

Amplifiers placed on common fiber


XL-PON architecture

< 30 km

OLT10Gbps / 2.5Gbps

One fiber for accessto all MAPs

1:512

EDFA, OADMTransponder

EDFA, OADMTransponder

MAP

MAPONT

ONT

OLT

all downstream and ONT upstream in C-band Low power consumption in amplification nodes

100 km


Burst Mode Receivers

• Burst Mode Receivers (BMRs) are a particular component situated in the OLT

• In XL-PON also the transponder at MAP (metro-access point) contains a BMR

• Function of the BMRs:

• Adaptation of the power intensity of each incoming burst

• Adaptation of the bit phase of each incoming burst

• Two main techniques for BMR: AC/DC coupling


OLT

ONU 1

ONU 2

ONU n

OLT

ONU 1

ONU 2

ONU n

BMR1

2

n1

2

n

Extinction

ratio

Loud/soft

ratio

1

2

n1

2

n

Extinction

ratio

Loud/soft

ratio

Burst Mode Receivers


Data lost Data received within BER limits

• DC component removed, AC threshold set at the midpoint (average) assuming even mark-space ratio

• Large change in burst amplitude requires finite settling time during which data will not be received

AC Coupling

LOUD BURST SOFT BURST

TIME

POWER

LEVEL


DC Coupling

• The decision threshold is not allowed to settle (and drift) based on the average power level

• The threshold is changed according to each burst amplitude

• Speeds up the potential settling time and ensuring effective immunity against long CIDs

• DC coupled front-ends are significantly more difficult to implement in practice than AC coupled designs (more unstable)


Edge Detection Technique

t

V Tbit

0

V

t0

t

V

0


Edge Detection Technique

• Means: the detection of the rising and falling edge of the signal pulses

• A differential output has to be produced after the optical signal has been detected. Once the edges have been detected, a high-speed comparator will discriminate the mark/spaces received

+Vcc

+-

Photodiode Trans-impedance

amplifier

Transientdetector

Comparator

A

PinERD(t)

C

R

f=RC

±Vth

Vc(t)V(t)

Vout(t)


Simulation Results

• Given a specific minimum holding time requirement, with a very small RC constant, the differentiated signal might be too narrow that the receiver miss it.

• On the other hand, with a very large RC constant, the capacitor may be able to fully discharge during the bit interval – the amplitude level won’t be reach! . There should be an optimum value then!

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14-0.5

0

0.5

1

1.5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14-1.5

-1

-0.5

0

0.5

1

1.5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14-0.5

0

0.5

1

1.5

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14-1.5

-1

-0.5

0

0.5

1

1.5


Experimental Results: Dynamic Range of 17 dB

EYE DIAGRAM OF LOUD BURST AFTER THE COMPARATOR

PRBS SIGNAL (+4dBm)

EYE DIAGRAM OF SOFT BURST AFTER THE COMPARATOR

PRBS SIGNAL (-13dBm)

Dynamic Range of 17 dB!!!


Experimental Results: Clock Recovery

• Clock Recovery Features:

• The technique is based around a phase-locked loop operating in a system at data rate of 2.488 Gbps

• Spectral analysis of the differentiated signal after the photodiode reveals well defined components that are directly related to the data rate of the system (burst and PRBS data).

• Any clock recovery scheme that utilized these peaks would be independent of data pattern


Experimental Results: Clock Recovery

Spectrum of the differentiated signal burst

Pattern of optical signal and clock recovery from the same signal at 2.5

Gbps


Conclusions

• AC/DC coupling are among the main techniques used nowadays for AC/DC coupling are among the main techniques used nowadays for BMRs.BMRs.

• Edge Detection is an alternative technique that overcomes the Edge Detection is an alternative technique that overcomes the disadvantages presented in AC/DC couplingdisadvantages presented in AC/DC coupling

• Edge detection technique is immune to baseline drift due to ac/dc coupling techniques, as shown by simulation and confirmed experimentally

• System performance is unaffected by long sequences of ones and zeros.

• The laboratory demonstrator currently under construction shows the functionality of the receiver at 2.5 Gbps over 32 km of fibre.

• An optical dynamic range of 17 dB has been achieved in the laboratory

• Edge detection technique removes the need of guard bands as data recovery is instantaneous

• Clock recovery of a differentiated burst can be achieved with a simple PLLClock recovery of a differentiated burst can be achieved with a simple PLL


ENDEND

muse xl-pon: general concept and approaches for burst-mode receivers emilio hugues salas university...

Documents

bb cluster meeting

fiber slide

unstable slide

user slide

xlpon characteristics

burst amplitude

xlpon objective

muse xlpon