All fiber, low threshold, widely tunable single-frequency, erbium-doped fiber ring laser with a tandem fiber Fabry–Perot filter

Abstract

An all fiber, widely tunable, single-frequency, erbium-doped fiber ring laser was constructed with a threshold pump power as low as 10 mW. Tuning over more than 30 nm was obtained by applying 0 to 17 dc V to an intracavity fiber Fabry-Perot filter. Threshold pump power versus wavelength data showed low variation over the tuning range. Mode hopping suppression with a tandem fiber Fabry-Perot filter is proposed and demonstrated. Stable single-frequency operation was demonstrated with side mode suppression higher than 35 dB.Single-frequency, widely tunable laser operation at the 1.5 pm window has potential applications in optical coherent communication systems. Due to its narrow linewidth and inherent compatibility with optical fiber, the erbium fiber laser is a promising candidate for use in these communication systems and has received considerable attention recently. Most efforts on the fiber laser, to date, have employed discrete optical components as part of the system. These systems suffered from either large cavity loss (thus large threshold pump power) ,112 small tuning range,314 or severe mode hopping. Recently, a temperature compensated, electronically tunable fiber Fabry-Perot (FFP) iilter was reported with low insertion loss and high tinesse.5 Here we demonstrate an all fiber, electronically tunable (1530-1560 nm with O-17 dc V), single-frequency erbium-doped fiber ring laser with a fiber Fabry-Perot wavelength selective element. Use of the fiber Fabry-Perot filter leads to improved threshold performance ( < 10 mW, 980 nm pumping) as compared to other wavelength tuning approaches demonstrated to date. Figure 1 shows the experimental setup. For the lirst part of our experiment, we investigated the behavior of our laser with a single broadband FFP (without the inset in Fig. 1). The 980 nm output of a titanium:sapphire (or diode) laser was coupled through a wavelength division multiplexer for the pumping source. The coupling efficiency was 50% and more than 60% of the pump power was absorbed after the 4.5-m-long piece of aluminumcodoped erbium fiber (BT&D, 50 ppm, 5 pm core diameter ) . A pig-tailed polarization-dependent isolator (isolation 35 dB) was used to prevent spatial hole burning caused by bidirectional operation for more stable singlefrequency operation. The isolator also served to block feedback from the output port of the system. A polarization controller (PC) was used to match the polarization state to the input polarization of the isolator. The polarizationdependent isolator and polarization controller can be replaced by a polarization-independent isolator. The wavelength selective element was a broadband fiber Fabry, Perot (FFP) filter with a 26.1 GHz (0.196 nm at 1.5 pm) bandwidth (FWHM) and a 4020 GHz free-spectral range (FSR). The total cavity loss was estimated to be less than 6.5 dB from a small-signal gain measurement and threshold data. The specific sources of loss were 2.5 dB from the FFP, 1 dB from the isolator, 1 dB from the wavelength division multiplexer and coupler, and 2 dB from...

Erbium‐doped integrated waveguide amplifiers and lasers

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Narrow-band erbium-doped fibre linear–ring laser

“…This approach ensures narrow-band lasing because there is no spatial hole burning effect. To obtain a spectrum of the order of several kilohertz in width or even narrower, use is commonly made of intracavity filters (such as narrow-band Fabry - Perot filters [7] and phase-shifted fibre Bragg gratings [6]). The simplest, and effective, way of narrowing a spectrum and improving emission stability is by using an unpumped active fibre section, which, in combination with a Bragg grating, forms a dynamic narrow-band filter with a transmission bandwidth in the order of several tens of megahertz [2,4,5].…”

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