Polarization sensors and controllers for coherent optical communication systems

In this invited tutorial review paper, I discuss the various options available to match the state of polarization of the signal and local oscillator waves in a coherent fiber optical communication system. The various advantages and disadvantages of each technique are discussed and directions for further work are identified. © 1987 SPIE

Single-mode fiber measurements

In this invited tutorial review paper on single-mode fiber measurements, I discuss the various methods used to characterize the following important transmission parameters of single-mode fibers: Attenuation, cut-off wavelength, mode-field diameter and chromatic dispersion. Single-mode fibers are being used increasingly in long-haul links and are even being considered for subscriber networks. © 1986 SPIE

Erbium-Doped Fiber Power Amplifiers with Pump Reflecting Mirrors in the 800 nm Band

The behavior of alumino-phosphate-silicate (APS) erbium-doped fiber power amplifiers (EDFA) for the various pump wavelengths, in the small signal and large signal regime, has been well studied with the 800 nm band pumping. It has already been shown that bidirectional pumping is more efficient especially at shorter wavelengths due to the presence of large excited state absorption (ESA). However, bidirectional pumping requires more components which can increase the complexity and cost of the system. In this letter, we have compared, using a computer model, the performance of power EDFA’s with a Bragg reflecting pump mirror etched at the output end of the fiber. For small pump powers (Pp≈ 10 mW) this configuration is better than bidirectional pumping, both for gain and noise figure (NF). At large pump powers (Pp≈200 mW) the output signal powers are comparable and the noise figure is better for the configuration with the reflecting mirror. © 1992 IEE

Polarization diversity and scrambling techniques for coherent systems

In this paper, we review polarization-diversity and polarization scrambling techniques and also include recent progress in these areas. The advantages and disadvantages of these techniques and several experimental and theoretical results reported to date are also discussed. © 1990 SPIE

Comparison of Forward and Bidirectional Pumping at 805 and 819 nm in Erbium-Doped Silica Fiber Amplifiers

Using an accurate and comprehensive computer model, we compare 805–810 and 819–825 nm band pumping of erbium-doped aluminosilicate fiber amplifiers. A comparison is made for both forward and bidirectional pumping over a wide range of pump powers. It is shown that 805–810 nm pumping is more efficient if bidirectional pumping is used, while 819–825 nm pumping is more efficient if only forward pumping is carried out. © 1991 IEE

Refractive Index and Material Dispersion Interpolation of Doped Silica in the 0.6-1.8 µm Wavelength Region

In this paper, we propose an extension of the Claussius- Mossotti interpolation scheme, so that the refractive index and material dispersion of GeO2 and F-doped silica glasses, with doping concentrations different than that of published data, can be predicted in the 0.6-1.8 µm wavelength region. The new interpolation expression provides a well-behaved functional relationship for use in computer models which analyze propagation in single-mode fibers. The technique proposed is particularly powerful because it can be applied to any glass, whether single or multicomponent, having any other single dopant. © 1989 IEE

Experimental measurement of gain in erbium-doped fluoride fiber amplifier in the 850-nm signal band

In this letter, we report an efficient single-mode Er3+ doped fluoride fiber amplifier (EDFFA) in the 850 nm signal band. The Ti-Sapphire laser was used to pump the EDFFA at 792 nm with an estimated absorbed pump power of 35 mW. The EDFFA used a 4.2 meter long NA = 0.39, λc = 850 nm fluoride fiber as the active medium. A peak gain of 25 dB was observed at 852 nm. The gain was measured for a 10 nm region between 847.5 nm and 857.5 nm. The 3 dB gain bandwidth is less than 4 nm. However, the gain exceeded 20 dB over wavelength region of at least 7.5 nm. The gain and the gain bandwidth can be further increased by optimizing the length of the active fiber

Temporal, spatial, and spectral modeling of erbium-doped fiber amplifiers

We discuss the methods and results of the temporal, spatial, and spectral modeling of doped fiber amplifiers. Particular emphasis is placed upon energy extraction with single pulse propagation

Pr\u3csup\u3e+\u3c/sup\u3e-doped fluoride fiber amplifiers: optimum design considerations

Waveguide parameters for Pr+-doped fluoride fiber amplifiers have been optimized for low and moderate values of relative refractive index difference. A cut-off wavelength of 750 nm gives maximum gain for NA = 0.1 and 0.2. A pump reflecting mirror etched at the output end of the amplifier gives higher gain at smaller lengths (≈ 1/3) in both the small and large signal regimes

Performance of erbium-doped fiber optical power amplifiers pumped in the 800-nm band

We use a comprehensive computer model to evaluate the performance of erbium doped optical power amplifiers (EDFA) in the 800 nm band. The pump wavelength dependence of the amplifier gain and noise is considered for aluminophosphate (APS-EDFA) and fluorophosphate (FP-EDFA). The existence of band optimum length, where the output remains constant and close to the peak output for a pump band, has been shown for both APS- EDFA and FP-EDFA under saturated conditions. It has been shown that band optimum length exists for both APS-EDFA and FP-EDFA unlike in the case of small signal gain, where the BOL existed only for APS-EDFA. The influence of the signal excited state absorption (ESA) at various pump powers and wavelengths is studied. The performance of power EDFAs with a pump reflecting mirror has been compared with bidirectional pumping and co-directional pumping for both APS-EDFA and FP-EDFA. For small pump powers (Pp ≈ 10 mW) the configuration with pump reflecting mirror is better than bi-directional pumping, both in terms of large signal gain and noise figure (NF) for APS-EDFA and FP-EDFA. At large pump powers (Pp ≈ 200 mW) the output signal powers are comparable and the NF is better for the configuration with the reflecting mirror for APS-EDFA. The signal gain and noise performance is better in the case of FP-EDFA even at Pp = 200 mW