BB Cluster Meeting – 20 th March 2007 Passive optical network (PON) Triple play = Data, VoIP and Video on the same fiber
BB Cluster Meeting – 20 th March 2007 PON technologies: overview TypeFormatMax. Data rateSplitreachBudget BPONATM0.6 GBps up, 1.2 GBps down1:6420 km (G)EPONEthernet1.2 GBps up & down1:1620 km GPONG.984.32.5 GBps down 1.2Gbps up1:6420 kmB+ : 28dB Standarisation: FSAN/ITU-T:NG-PON 10G/2.5G then 10G/10G, ~2010 IEEE:10G/1G then 10G/10G, target ~ 10km, 16 user
BB Cluster Meeting – 20 th March 2007 Objective of XL-PON: Reduction of network elements BRAS OLT
BB Cluster Meeting – 20 th March 2007 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 100s of users minimize system cost due to long-reach
BB Cluster Meeting – 20 th March 2007 XL-PON Characteristics: Power budget situation Attenuation in an XL-PON: Splitter: 35dBat 1:1024 Fiber: 0,25 dB / km 25dBat 100km Total: 60dB Power budget by transmitter and receiver at 10Gbit/s: < 20dB Up to 40dB of amplification required!
BB Cluster Meeting – 20 th March 2007 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,...)
BB Cluster Meeting – 20 th March 2007 XL-PON architecture < 30 km OLT 10Gbps / 2.5Gbps One fiber for access to all MAPs 1:512 EDFA, OADM Transponder MAP ONT OLT all downstream and ONT upstream in C-band Low power consumption in amplification nodes 100 km
BB Cluster Meeting – 20 th March 2007 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
BB Cluster Meeting – 20 th March 2007 OLT ONU 1 ONU 2 ONU n OLT ONU 1 ONU 2 ONU n BMR 1 2 n 1 2 n Extinction ratio Loud/soft ratio 1 2 n 1 2 n Extinction ratio Loud/soft ratio Burst Mode Receivers
BB Cluster Meeting – 20 th March 2007 Data lostData 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 BURSTSOFT BURST TIME POWER LEVEL
BB Cluster Meeting – 20 th March 2007 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)
BB Cluster Meeting – 20 th March 2007 Edge Detection Technique t V T bit 0 V t0 t V 0
BB Cluster Meeting – 20 th March 2007 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 + - PhotodiodeTrans- impedance amplifier Transient detector Comparator A Pin ER D(t) C R f =RC ±V th V c (t)V(t) V out (t)
BB Cluster Meeting – 20 th March 2007 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 wont be reach!. There should be an optimum value then!
BB Cluster Meeting – 20 th March 2007 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!!!
BB Cluster Meeting – 20 th March 2007 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
BB Cluster Meeting – 20 th March 2007 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
BB Cluster Meeting – 20 th March 2007 Conclusions AC/DC coupling are among the main techniques used nowadays for BMRs. AC/DC coupling are among the main techniques used nowadays for BMRs. Edge Detection is an alternative technique that overcomes the disadvantages presented in AC/DC coupling Edge Detection is an alternative technique that overcomes the disadvantages 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 PLL Clock recovery of a differentiated burst can be achieved with a simple PLL