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The International Society for Optical Engineering

We report on the improved OSNR monitoring technique for WDM networks using the polarization-nulling method. Unlike the previous techniques based on the polarization, the proposed technique was not sensitive to PMD and nonlinear birefringence.

OSNR Monitoring Technique basde on Polavization - Nulling Method

A single-measurement sweep-free distributed Brillouin optical time domain analyzer (BOTDA) sensor based on phase detection is proposed and experimentally demonstrated employing digital optical frequency comb (DOFC) probe signal. Brillouin Phase Spectrum (BPS) of DOFC probe induced by Brillouin interaction is measured using coherent detection in a single acquisition, without any frequency scanning and data averaging. Single-measurement BOTDA sensor based on BPS in 10km long fiber is demonstrated with a response time of 100 μs, which is limited only by the fiber length. The spatial resolution is 51.2m, determined by the duration of DOFC. And the Brillouin frequency shift (BFS) uncertainty is estimated to be~1.5 MHz at the end of fiber under test (FUT). Benefiting from the fast response time, dynamic measurement up to 1 kHz vibration frequency has been demonstrated.

Single-measurement digital optical frequency comb based phase-detection Brillouin optical time domain analyzer.

Polarization noise arises in Brillouin optical time-domain analysis due to the strong polarization sensitivity of stimulated Brillouin scattering. To avoid this noise, it turns out to be indispensable to perform some kind of polarization scrambling, either in the pump pulse, the probe signal or both. This is usually achieved using polarization scrambling/switching systems, which, being mechanical, tend to be not as robust as it would be desirable. In this paper, we propose a completely passive system, with no moving parts, to eliminate polarization noise in a BOTDA. It is based on the use of passive depolarization of the pump pulse together with balanced detection among orthogonally polarized Stokes and anti-Stokes bands of the probe signal. The setup requires no alignment readjustment over time and provides a performance similar to a conventional BOTDA using scrambler.

/pdf/simple-method-for-the-elimination-of-polarization-noise-in-2gwzcp72t1.pdf

Simple Method for the Elimination of Polarization Noise in BOTDA Using Balanced Detection and Orthogonal Probe Sidebands

We propose and experimentally demonstrate a chromatic dispersion (CD)-insensitive first-order polarization mode dispersion (PMD) monitoring method based on radio-frequency (RF) power measurement. In high-speed (>10-GSym/s) transmission systems, a narrowband fiber Bragg grating (FBG) notch filter filters out the optical components at 10GHz away from the carrier. After square-law detection, the 10-GHz RF tone changes with PMD and is insensitive to CD, which can be used as a PMD monitoring signal. Compared with the monitoring techniques utilizing clock tone, the PMD measurement range is increased from 26.3-ps to 50-ps while the requirement of the bandwidth of photodetector is reduced from 19GHz to 10GHz in 19-Gsym/s systems. It is experimentally shown that this technique is efficient on CD-insensitive first-order PMD monitoring for 38-Gbit/s DQPSK and 57-Gbit/s D8PSK systems.

/pdf/cd-insensitive-pmd-monitoring-based-on-rf-power-measurement-wqed3m87tt.pdf

CD-insensitive PMD monitoring based on RF power measurement.

We propose and experimentally demonstrate a chromatic-dispersion (CD) monitoring method based on radio-frequency (RF) clock power ratio measurement in 38-Gb/s nonreturn-to-zero differential quadrature phase-shift keying (NRZ-DQPSK) and 57-Gb/s NRZ differential 8-level phase-shift keying (D8PSK) systems. A narrowband fiber Bragg grating (FBG) notch filter is centered at the optical carrier wavelength, such that the RF clock power decreases with CD. On the other hand, RF clock power increases with CD in the absence of the notch filter. By using the RF power ratio of the filtered and nonfiltered signals, polarization-mode-dispersion (PMD) effects on RF power ratio can be eliminated and CD measurement sensitivity can be increased. The CD monitoring range is 0 ~ 250 ps/nm in the systems with a symbol rate of 19-Gsym/s. Moreover, the proposed CD-monitoring method is not affected by received optical power.

PMD-Insensitive CD Monitoring Based on RF Clock Power Ratio Measurement With Optical Notch Filter

We propose and demonstrate a novel method to suppress the polarization induced signal fluctuation in Brillouin Optical
Time Domain Analysis (BOTDA) fiber distributed sensing system. The polarization diversity scheme contains two
polarization beam splitters (PBSs) and a piece of single mode fiber (SMF). The pulsed pump wave is split into two
beams with orthogonal polarization states and one of the beams is delayed by a time related to the pulse width. Then, the
two beams are recombined. Theoretically, the Degree-of-Polarization (DOP) of the recombined wave is zero and the
distributed sensing system is insensitive to the polarization state of the probe. Stable distributed temperature
measurement is demonstrated along a 1.2 km SMF.

Suppression of polarization sensitivity in BOTDA fiber distributed sensing system

We propose a scheme on broadband multi-wavelength light source generation based on phase modulation in a ring. 125-channel light source with channel spacing of 10-GHz is demonstrated using a single phase modulator in a loop.

Broadband multi-wavelength light source generation using a single phase modulator in a loop

We propose a technique on chromatic dispersion (CD) monitoring based on RF power ratio measurement. Both simulation and experimental results show that the method is efficient on eliminating polarization-mode dispersion (PMD) effects in CD measurement.

Jing Yang

Papers

CD-insensitive PMD monitoring based on RF power measurement.

PMD-Insensitive CD Monitoring Based on RF Clock Power Ratio Measurement With Optical Notch Filter

Suppression of polarization sensitivity in BOTDA fiber distributed sensing system

Broadband multi-wavelength light source generation using a single phase modulator in a loop

PMD insensitive CD monitoring based on RF power ratio in D8PSK and DQPSK systems