A novel L-band multiwavelength mode-locked semiconductor fibre laser

Abstract

ABSTRACT We present a multiwavelength mode-locked fiber ring laser incorporating a semiconductor optical amplifier (SOA) and a Fabry-Perot semiconductor optical amplifie r (FP-SOA). SOA is mode-locked by an injected external optical signal, act as loss modulator, and FP-SOA serves as a tunable comb filter. Our laser source can generate 19 synchronized wavelength channels with the extinction ratio of about 21 dB , each mode-locked at 10 GHz, and modelocked pulse width is about 40 ps. Oscillation wavelengths band and wavelength spacing can be tuned by adjusting bias current and a tunable optical delay line (ODL) or a temperature controller, respectively. Polarization insensitive devices ensure that the output power is rather stable. Keywords: Optical communications; mode-locked lasers; semiconductor optical amplifier (SOA); Fabry-Perot semiconductor optical amplifier (FP-SOA) 1. INTRODUCTION Multiwavelength ultrashort optical pulse source is attractive since it has widespread applications in optical sensing, optical instrumentation, microwave generation, optical signal processing, and high speed optical signal transmission. A large number of approaches have been taken to generate multiwavelength outputs simultaneously, include multiwavelength erbium-doped fiber lasers [1, 2], multiwavelength Raman lasers [3, 4], and semiconductor optical amplifiers (SOAs) fiber lasers [5, 6]. However, due to homoge neous broadening of lasing modes in Er-doped fibers laser, it is difficult to obtain stable multiwavelength light sources. To suppress homogeneous broadening of lasing modes, multiwavelength Er-doped fiber lasers were immersed in liquid nitrogen [7]. In addition, Raman lasers have the advantage for multiwavelength emission over extremely large bandwidth, but, high-power semiconductor laser diodes being fit for various wavebands still need to be developed. Since the SOA has the property of primarily inhomogeneous broadening, it can support simultaneous oscillation of many lasing wavelengths. SOA-based multi-wavelength fiber lasers exhibit stable operation without any assistant measures. The need to extend the bandwidth of dense WDM systems has resulted in research to new transmission waveband, such as longer waveband (L-band, 1570 to 1610nm) within the low-attenuation window. Recently, a single wall nanotube (SWNT) -polyvinyl alcohol (PVA) saturable absorber with a 340 nm wide absorption band peaked at 1600 nm was utilized to realize an ultrafast mode-locked EDF laser in the L- band. This produces 498 fs pulses with a repetition rate of