Fault Localization of PON

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Fault Localization of PON

• Yeung Chue Hei (1008620051)Lam Yi Kwan
  (1008627154)

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Network Structure

• FTTX (fiber to the X)
• Passive (PON)
• Multiplexing (?P2MP)
• TDM
• WDM

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Goals

• Maintain service quality
• 1/3 of service disruptions are due to fiber cable
• Fault can be a disaster
• Assisting reparation
• Reduce lost
• Efficiency
• Not affecting the other service

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Challenges

• High resolution VS high DR capabilities
• Measurement time
• Point-to-multipoint problem

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Solutions for TDM-PONs

• P2P
• Active By-pass
• Passive By-pass
• Integrated OTDR functionality
• P2MP
• Tunable OTDR and wavelength selective reflectors
• Conventional OTDR and controlled reference
  reflections
• Brillouin OTDR

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Solutions for WDM-PONs

• Tunable OTDR/multi-wavelength source and optical
  reflector
• Re-using existing light sources
• Commercial multi-wavelength OTDR

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Other solutions

• Optical Code-division Multiplexing
• Optical Frequency Domain Reflectometry

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Measuring the Individual Attenuation Distribution
of Passive Branched Optical Networks

• Kuniaki Tanaka, Mitsuhiro Tateda, Senior Member,
  IEEE, and Yasuyuki Inoue, Member, IEEE
• IEEE PHOTONICS TECHNOLOGY LETTERS, VOL 8, NO 7,
  JULY 1996

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Reference Reflector
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Reference Reflector

• Conventional OTDR
• Specially designed branched networks
• Transmission line lengths differ with each other
• Cannot test branched fiber losses individually
• Go to the subscriber terminals after branching
  and measure the transmission loss directly

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Passive By-pass
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New method
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Arrayed Waveguide Grating (AWG)
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Optical Splitter/Router Module
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Optical Splitter/Router Module
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Optical Splitter/Router Module
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OTDR Configuration
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OTDR Traces
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Fiber Fault Identification for Branched Access
Networks Using a Wavelength-Sweeping Monitoring
Source

• Chun-Kit Chan, Frank Tong,Lian-Kuan Chen,
  Keang-Po Ho, Dennis Lam

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Introduction

• Conventional OTDR cannot differentiate Rayleigh
  backscattered light from different branches
• Multiwavelength OTDR is expensive

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Fiber Identification Scheme
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• To avoid pulse collision
• (2nL/c) lt 1/(Nf)
• Eg. N8, f1kHz, n1.5, max L12.5km

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Experiment

• 1 x 4 branched optical network
• Data channels 1548nm, 1551nm
• 1Gb/s 210-1 PRBS NRZ
• L18.8km, L2L36.6km, L4 is unmonitored
• FBG 1556.4nm, 1558nm, 1559.7nm
• 3dB passband 0.4nm, 0.8nm, 0.9nm
• Sawtoothed signal 2kHz

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Summary

• Makes use of FBGs
• No additional monitoring source
• Both time and frequency domain
• With OTDR techniques, can locate exact fiber cut
  position

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QA

• Thank you for your attention!

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Active by-pass
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Passive by-pass
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Global analysis
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Tunable OTDR and Wavelength Selective Reflector
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Tunable OTDR and Wavelength Selective Reflector
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Tunable OTDR and Wavelength Selective Reflector
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Controlled reference reflections with convention
OTDR
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Brillouin OTDR (BOTDR)
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Tunable OTDR/multi-wavelength source and optical
reflector
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Re-using existing light sources
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Commercial multi-wavelength OTDR
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OTDR
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Principle of OTDR Operation

• Launch short duration light pulses into a fiber
  and then measure the optical signal returned to
  the instrument.

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Block Diagram of OTDR
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OTDR Fiber Signature
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Features

• Straight lines
• distributed Rayleigh backscattering
• Positive spikes
• discrete reflections
• Steps
• bends or splices

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Events

• Reflective events
• Fresnel reflections
• Mechanical splices
• Connectors
• Cracks
• Non-reflective events
• Bends
• Fusion splices

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Dynamic Range
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Attenuation and Event Dead Zone
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Attenuation dead zonevs OTDR receiver bandwidth
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DR and Dead zone

• High dynamic range mode
• larger pulse width
• increasing the strength of the received signal
  ,better DR, better sensitivity
• larger dead zonelower resolution
• High resolution mode
• smaller pulse width
• smaller DR, less sensitive
• smaller dead zonehigher resolution

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Ghost Events

• echoes generated by multiple reflections
• only solution avoid high reflectivity connectors
• Dirty or scratched connectors
• the repetition rate of the laser pulses is too
  fast (echoes from consecutive pulses may overlap)

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Ghost Events
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Gainer Event

• If the backscatter after the loss event is higher
  than before the event, a gainer will occur.
• Backscatter information does not always precisely
  indicate what happens to a forward traveling
  signal.

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Remote Fiber Test System

• Remote test unit, control unit
• Optical test access unit
• share on test equipment
• Controlled by computer
• databases and computing algorithm.
• Reference file
• created and saved in the data base