A.S. Siddiqui

Analysis of optical gain enhanced erbium-doped fiber amplifiers using optical filters

Erbium-doped fiber amplifiers (EDFAs) with enhanced optical gain obtained by incorporating narrow-bandpass optical filters into the amplifier length are studied. It is shown in theory that it is possible to increase optical gain by more than 10 dB for optical signals around the wavelength of 1.55 mu m, compared with conventional EDFAs without filters. It is also shown that the gain improvement at longer wavelengths away from the amplifier gain peak is much higher than that of the EDFA with an optical isolator within the amplifier length. The optimum filter position is found to be around 42% of the total amplifier length from the input end. The effects of filter insertion loss and pump loss are discussed. This amplifier can be used as an optical preamplifier in a receiver for a wide range of wavelengths.<<ETX>>

Fully polarimetric optical time-domain reflectometer with 1-m spatial resolution

In this paper, we make the first report of what we believe is the first fully polarization-sensitive, real-time optical time domain reflectometer (OTDR), which can measure the full polarization-scattering matrices along the fiber, leading to the evaluation of both the linear- and twist-induced circular birefringence distributions along the fiber. This enables the PMD properties to be evaluated for fibers exhibiting both types of birefringence as well as identifying fiber sections with or without twist.

Theoretical analysis and measurement of the effect of fiber twist on the polarization OTDR of optical fibers

With the growing interest in polarization-mode dispersion (PMD), the technique of polarization optical time domain reflectometry (POTDR) has received attention because of its ability to measure birefringence characteristics along a fiber. PMD measurements using POTDR normally assume that the linear birefringence /spl beta//sub L/ is the dominant birefringence in the fiber, such that the circular birefringence /spl beta//sub C/ can be ignored, allowing the PMD due to /spl beta//sub L/ to be inferred from the periodicity of the POTDR output. In this paper we induce circular birefringence by fiber twist and show that even small values of /spl beta//sub C/ will have a considerable influence on the POTDR output and can lead to an overestimate of the fibers PMD.

An accurate numerical model for distributed Raman amplifiers

We present, for the first time, a complete numerical analysis of Raman amplifiers including pump depletion and higher-order Stokes wave generation. Raman gain and OSNR in co-propagating, counterpropagating and bi-directionally pumped FRAs are examined.

Polarization shaped duobinary transmission scheme

We present a novel duobinary transmission scheme exhibiting a symmetrical eye degradation and tolerance to chromatic dispersion and fiber nonlinear effects. Simulations show that the maximum attainable dispersion-limited transmission distance for 10-Gb/s data over standard single-mode fiber can be extended to 160 km for a 1-dB eye closure penalty. We compare the performance of this scheme with phase-shaped duobinary transmission, and conclude that in a practically realizable system, polarization-shaped duobinary will perform better.

Analytical description of backscattered states of polarization in polarization optical time-domain reflectometry measurements on uniformly twisted linearly birefringent optical fiber

We present a detailed derivation of the locus of Rayleigh backscattered states of polarization for polarization optical time domain reflectometry in uniformly twisted optical fiber with intrinsic linear birefringence. The locus is algebraically a quartic whose topology is determined by the relative orientation on the Poincaré sphere of the input SOP and the effective birefringence vector. We present an analysis that indicates how experimental data may be interpreted, through geometric parameters of the locus, for evaluating the fiber parameters. The analysis also indicates the minimum number of experimental data points required for meaningful values for the fiber parameters to be obtained.

Dispersion tolerant transmission using a duobinary encoded polarization shift keying modulation format

We experimentally demonstrate a novel modulation format based on a combination of polarization shift keying and duobinary encoding. This format achieves a dispersion limited transmission distance three times greater than that for binary IMDD modulation.