title: Correlation-based OTDR for in-service monitoring of 64-split TDM PON.
abstract: We demonstrate that the correlation-based optical time domain reflectometer (OTDR) can be used for the in-service monitoring of the 64-split time-division-multiplexed passive optical network (TDM PON). To achieve this objective, we superimpose a pseudo noise (PN) sequence having a modulation depth of ~40% to the downstream signal and utilize it for the correlation detection. However, the use of such a large PN sequence can seriously deteriorate the performance of the downstream receiver. Thus, we apply 8B/10B encoding to the downstream signal, and then filter out the PN sequence at the downstream receiver by using a high-pass filter. As a result, the power penalty caused by the use of a large PN sequence is reduced to an acceptable level (<3 dB), while the dynamic range of this correlation-based OTDR is increased to ~30 dB. We then evaluate the performance of the proposed OTDR in the fiber link similar to the optical distribution network of the 64-split TDM PON. The results show that this OTDR can detect both the reflective and non-reflective events occurred in the feeder fiber as well as the reflective events in the drop fibers even in the 64-split TDM PON.
authors.affiliation: Department of Electrical Engineering, Korea Advanced Institute of Science and Technology 335 Gwahangno,Yuseong-gu, Daejeon 305-701, Korea.
authors.forename: H K
authors.initials: HK
authors.lastname: Shim
authors.forename: K Y
authors.initials: KY
authors.lastname: Cho
authors.forename: Y
authors.initials: Y
authors.lastname: Takushima
authors.forename: Y C
authors.initials: YC
authors.lastname: Chung
mesh_terms: D000465:Algorithms; D003195:Computer Communication Networks / Q000295:instrumentation*; D004867:Equipment Design; D019544:Equipment Failure Analysis / Q000295:instrumentation*; D005336:Fiber Optic Technology / Q000295:instrumentation*; D010783:Photometry / Q000295:instrumentation*; D013685:Telecommunications / Q000295:instrumentation*