Reduction of gain depletion and saturation on a Brillouin–erbium fiber laser utilizing a Brillouin pump preamplification technique

This paper presents the characteristics of a multiwavelength L-band Brillouin–erbium comb fiber laser with a preamplified Brillouin pump (BP) power technique at low pumping powers. The issue of erbium-doped fiber gain depletion and Brillouin gain saturation are resolved by the proposed structure. For long single-mode fiber length, the Stokes line emission occurs at low pumping powers because of the high strength of spontaneous Brillouin scattering, which provides a strong seed for coherent regenerative amplification of the Stokes line in the laser cavity. The laser structure achieves a low threshold power of 17 mW and is able to produce high number of output channels at low pumping powers. We experimentally show that the fiber laser structure can produce up to 37 channels at 55 and 0.045 mW of 1480 nm pump and BP powers, respectively

Characteristics of multiple wavelengths L-band Brillouin-erbium comb fiber laser at low pumping powers

This paper presents the characteristics of multiple wavelength L-band Brillouin-erbium comb fiber laser with intra-cavity pre-amplified Brillouin pump power technique at low pumping powers. The issue of EDF gain depletion and Brillouin gain saturation are resolved by the proposed structure. The laser structure achieves a low threshold power and is able to produce high number of output channels at low pumping powers. It produces up to 33 channels at 50 mW and 0.042 mW of 1480 nm pump and Brillouin pump powers, respectively

Multi-wavelength L-band Brillouin-erbium comb fiber laser utilizing nonlinear amplifying loop mirror

In this paper, we demonstrate a novel multiwavelength L-band Brillouin–erbium fiber laser utilizing nonlinear amplifying loop mirror. The erbium-doped fiber section in the fiber loop mirror provides efficient amplification of Brillouin pump (BP) to generate the stimulated Brillouin scattering in the single-mode fiber coil. The laser structure can achieve symmetry breaking of the loop without requirements to an asymmetric coupler or polarization controller. The proposed fiber laser has a low threshold power of about 10 mW to create the first Brillouin–Stokes signal. The maximum number of 27 Stokes signals with a spacing of 0.089 nm is achieved by setting the BP wavelength at 1604 nm and its BP power is set at 2.2 mW

Compact wideband multilayer microstrip coupled lines bandpass filter for X-band application

A wideband bandpass filter for X-band application using multilayer microstrip coupled lines is presented in this article. Strong coupling required for wideband filter is realized by arranging multiple layers of microstrip lines on two different dielectric substrates and by overlapping these lines. The filter is fabricated on 0.254 mm thickness R/T Duroid 6010 and R/T Duroid 5880 with dielectric constant 10.2 and 2.2, respectively, by using standard photolithography process. Good results are obtained where the frequency responses exhibit that the filter successfully covers whole X-band frequencies by producing 44% bandwidth at 10.2 GHz center frequency with fifth-order Chebyshev response. Measured responses show good agreement with the simulated responses. The measured insertion loss for the multilayer filter is better than 2.5 dB, and the passband return loss is better than −12.4 dB. ©2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 448–450, 2010; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/mop.2491

Broadly tunable L-band multiwavelength BEFL utilizing nonlinear amplified loop mirror filter.

We demonstrate a widely tunable L-band multiwavelength Brillouin-erbium fiber laser utilizing a nonlinear amplified fiber loop mirror filter (AFLMF). By manipulating polarization controllers placed in the fiber loop, the erbium peak gain spectrum is able to be shifted. The nonlinear AFLMF induces wavelength-dependent cavity loss and serves as an amplitude equalizer. In addition, it provides flexibility on controlling the amount of light reflected and transmitted into and out of the laser's cavity. By utilizing 100 mW 1480 nm pump and 1.1 mW Brillouin pump power, an average of 24 stable output channels are generated by the proposed structure that could all be tuned over the whole L-band window from 1570 nm to 1610 nm

Widely tunable linear-cavity multiwavelength fiber laser with distributed Brillouin scattering.

We demonstrate a multiple wavelength Brillouin/erbium fiber laser in a linear cavity configuration. The laser cavity is made up of a fiber loop mirror on one end of the resonator and a virtual mirror generated from the distributed stimulated Brillouin scattering effect on the other end. Due to the weak reflectivity provided by the virtual mirror, self-lasing cavity modes are completely suppressed from the laser cavity. At Brillouin pump and 1480-nm pump powers of 2 and 130 mW, respectively, 11 channels of the demonstrated laser with an average total power of 7.13 dBm can freely be tuned over a span of 37-nm wavelength from 1530 to 1567 nm

High-gain erbium-doped fiber amplifier incorporating a double-pass amplification technique as a preamplifier

We present a high-gain erbium-doped fiber amplifier to be utilized as a preamplifier. A double-pass amplification technique is used in the first-stage amplifier together with a tunable bandpass filter. The secondstage amplifier is a counter-pumped configuration and another tunable bandpass filter is utilized to filter out amplified spontaneous emission from the first-stage amplifier. This design is able to produce a high gain of 55.6 dB and a noise figure of 6.02 dB at 1530 nm with a signal power of −45 dBm. The receiver sensitivity measurement shows that the proposed amplifier improves the minimum detectable power from −33.7 to −40.8 dBm for a bit-error rate of 10−11 at 155 Mbps

Enhanced structure of a double-pass erbium-doped fiber amplifier for multiple wavelength amplifications.

We demonstrate an enhanced double-pass erbium-doped fiber amplifier for multichannel amplification. The multichannel selection is formed by combining a demultiplexer and a multiplexer together in the fiber-loop mirror. The structure is able to filter out the amplified spontaneous emission that saturates the amplifier gain in the small signal regime. The maximum average gain of 47.2 dB is obtained with a gain enhancement of 12.8 dB at a -50-dBm signal power per channel. The noise figure penalty is almost negligible for a signal power per channel of less than -15 dBm

Novel compact “via-less” ultra-wide band filter utilizing capacitive microstrip patch

This paper presents a novel compact “via-less” UWB filter derived from a quarter-wavelength short-circuited stubs model. In this compact “via-less” UWB filter, there is no connecting vias as short circuit elements. Unlike its previous model that has 5 short-circuited stubs, this novel shape consists of two pairs of stubs which are joint together to share on the same microstrip patch and thus reduces total size of the UWB filter itself making it more compact in nature. With proper width optimization, the microstrip patch is able to decouple and provides low impedance to the ground in the UWB frequencies range. The filter delivers 3.85GHz to 10.44 GHz frequency range with 92.23% of fractional bandwidth. The magnitude of insertion loss is below than 0.53 dB and the return loss is lower than −14.8dB in the passband frequencies. The −3 dB bandwidth is from 3.85 GHz to 10.44 GHz with 92.23% of fractional bandwidth. The group delay only varied by 0.47 ns in the passband, which makes it suitable for radio communication systems

Compact 'butterfly' microwave ultra-wideband filter

In this paper, a compact 5 poles Ultra-Wideband (UWB) microwave filter is designed by using a quarter wave short-circuited stubs. The UWB filter bandwidth is covered from 2.75 GHz to 10.0 GHz. This filter designed is developed from a Low Pass Chebychev prototype with a 0.1 dB passband ripple. The first pattern layout uses 5 vias connecting to the ground. This pattern layout is then re-arranged to reduce the total area space needed on microstrip by maintaining the optimum filter response. Finally, a compact microwave filter with 21 mm X 16.1 mm dimension is presented here with excellent scattering characteristic results