Polarization Dependence Of Gain Research Articles

Polarization dependence of gain and amplified spontaneous Brillouin scattering noise analysis for fiber Brillouin amplifier**Project supported by the National Natural Science Foundation of China (Grant Nos. 61531003, 61690195, 61701040, and 61427813), the Fund of State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications (BUPT), China, and the Youth Research and Innovation Program of BUPT,

The polarization dependences of gain and amplified spontaneous Brillouin scattering (ABS) noise for fiber Brillouin amplifier (FBA) are analyzed through theories, simulations, and experiments. Modified vector propagation equations for calculating the gain of the probe signal and the ABS noise are derived and analyzed in the Stokes spaces. In simulations and experiments, we prove that the gain of the probe signal and the ABS noise are strongly dependent on the relative state of polarization (SOP) of the pump and probe signals. The closer the relative SOP of the pump and probe signals is, the more obvious ABS noise suppression effect will be brought by increasing the power of the input probe signal.

Efficient Pump Depolarizer Analysis for Distributed Raman Amplifier With Low Polarization Dependence of Gain

This paper discusses a method of reducing the polarization dependence of gain (PDG) of a distributed Raman amplifier. Reducing its PDG is important for a Raman amplifier because it is higher than that of an erbium-doped fiber amplifier and can degrade transmission performance. Raman PDG is determined primarily by two factors, namely 1) polarization-mode dispersion (PMD) of the transmission fiber and 2) degree of polarization (DOP) of the pump source. The authors propose a simple analytical model to show the required pump light DOP for a given transmission fiber's PMD and the allowable PDG. For instance, a low pump DOP of 5% produces a low PDG of 0.2 dB under typical fiber PMD conditions, in which the analytical model agrees well with experiment. Subsequently, to achieve the required DOP, the pump source configuration is investigated in detail. The authors used one length of polarization-maintaining fiber (PMF) as an efficient pump depolarizer and evaluated its performance for various pump light spectra. It has been shown that the DOP following the depolarizer is determined simply by Fourier transformation of the pump light spectrum. The analysis in this paper has led to the important result that a Fabry-Perot laser diode pump with a short piece of PMF is effective in achieving a low pump DOP due to its multimode spectrum when the length of the PMF is properly adjusted for the longitudinal-mode spacing frequency. It has been verified that a Raman amplifier's PDG can be reduced by the proposed efficient depolarizer sufficiently for a PDG-reduced Raman amplifier repeater to be applicable to long-haul transmission systems

Effects of Polarization-Mode Dispersion in Dual-Pump Fiber-Optic Parametric Amplifiers

Effects of polarization-mode dispersion (PMD) on dual-pump parametric amplifiers are investigated numerically using a set of four vector equations. It is found that PMD induces large fluctuations in the signal power that can affect the system performance by enhancing the outage probability. The average gain itself is reduced by more than 10 dB even for a relatively small value of 0.05 ps//spl radic/km for the PMD parameter. For larger values of the PMD parameter, the gain spectrum begins to distort and loses its flatness. We also show that the polarization dependence of gain cannot be eliminated by using orthogonally polarized pumps.

Fabrication and complete characterization of polarization insensitive 1310 nm InGaAsP–InP quantum-well semiconductor optical amplifiers

Polarization insensitive 1310 nm InGaAsP–InP multi-quantum-well (MQW) semiconductor optical amplifiers (SOAs), with 7° tilted ridge waveguide and buried-window end facets, have been fabricated and fully characterized on chip and module level. SOAs chips with an optimized complex strained MQW active region exhibited less than 1 dB polarization dependence of amplified spontaneous power in the drive current range of 50–200 mA. The amplifier module, having a residual facet reflectivity of 2.8 × 10−5, achieved 25 dB fibre-to-fibre unsaturated gain, for both transverse electric and transverse magnetic polarization states, 11.2 dBm saturation output power, and 7.6 dB noise figure at 1310 nm. The polarization dependence of gain was less than 0.6 dB in the 3 dB gain bandwidth of 56 nm. Coupling efficiency played a significant role in the gain, saturation output power and noise figure of a SOA module. Spot-size-converter integrated SOAs with buried heterostructures are expected to exhibit further improved performances.

Polarization dependence of gain in discrete Raman amplifiers with dispersion compensating fibres

Polarization dependence of stimulated Raman scattering is a fundamental physical effect, which influences the design and application of Raman amplifiers for optical networks. We report experimental data of the study of polarization dependence of Raman gain in dispersion compensating fibres (DCF). The investigation displays a strong variation of the polarization dependence of Raman gain versus average polarization mode dispersion (PMD) values of DCF for both co-propagating and counter-propagating pump configurations. The reported data show, for the first time to our knowledge, that, for large PMD values, such a dependence may be as small as to be comparable with the accuracy of the measurements. The results of the study may be used to simplify the design of Raman amplifiers to avoid depolarization of pump sources that are currently used to decrease polarization dependence of Raman gain.

Spot-size converted polarization-insensitive SOA gate with a vertical tapered submicrometer stripe structure

To develop polarization-insensitive semiconductor optical amplifier (SOA) gates into more efficient and functional optical components by using hybrid integration with a planer lightwave circuit (PLC) platform, vertical tapered spot-size converters were integrated into a SOA gate with a narrow mesa-stripe structure of submicrometer width leading to low coupling loss (2.6 dB). Very-low polarization dependence of gain ( 30 dB) were achieved in a wide wavelength range (40 nm). High-speed (<1 us) gate operation was also demonstrated. These results indicate that the spot-size converted SOA integrated on a PLC platform will perform well in wavelength-division-multiplexing (WDM) applications.

Polarization dependence of gain in stimulated Raman scattering.

We present a new, rotationally invariant formalism for the theory of stimulated Raman scattering. The formalism is applied to Raman transitions of well-defined rotational symmetry, e.g., rotational Raman (Stokes) transitions, yielding the explicit dependence of gain on light polarization, phase mismatch, and frequency offset.