1.58-μm band gain-flattened erbium-doped fiber amplifiers for WDM transmission systems

Abstract

doped fibers are cascaded and the external injected C-band signal is employed as a secondary pump source. Approximately 7.5-dB gain improvement is achieved for the short EDF. The gain improvement of L-band EDFA through the C-band laser injection depends on the injection wavelength, namely, the power transfer efficiency from C-band to L-band. A tradeoff necessary to realize gain enhancement and noise characteristic improvement is confirmed from the experimental results. The experimental results imply that the suggested EDFA approach is capable of implementing the gain enhancement in the short erbium-doped fiber and a lower 980-nm pump power. From our viewpoint, therefore, this scheme will provide a promising and cost-effective approach in the development of practical L-band EDFAs. ACKNOWLEDGMENTThis work was supported by Chinese Natural Science Foundation under grant no. 60177015. INTRODUCTIONThe local oscillator in a wireless transceiver has to satisfy many challenging requirements, such as low phase noise, wide-tuning, and quadrature signal generation [1,2]. Recently, wide tuning features have been in high demand, due to the generalization of multi-band transceivers and the wideband natures of the future generation transceivers, such as software defined radios. Satellite and cable-TV receivers are another application that requires wide tuning VCO. The ever-increasing wireless communication market drives the need for better integration of personal communication transceivers in order to meet lower cost, smaller form factor, and lower power dissipation.Ring oscillators are one of the most popular wide tuning topologies. They are generally used in monolithic form, and provide a wide range of oscillation frequency by controlling the bias currents or the value of passive components, such as resistance or capacitance. They are also simpler than other oscillators and can easily operate at high frequencies implemented in standard CMOS technology. However, ring oscillators tend to show high phase noise compared to, for example, the LC-tuned oscillator. Lately, ring oscillators that adopt LC-tuning have been reported [3,4]. Although the LC-tuning improves phase noise considerably, their performance is still worse than that of conventional LC-tuned oscillators. Besides, the tuning ranges of the LC-tuned ring oscillators are poorer than the classical ring oscillators.The typical monolithic LC-tuned oscillators tend to offer poor tuning range, as the tuning relies on the on-chip varactors. Commonly used monolithic varactors are the p-n junction, and inversion-and accumulation-mode MOS capacitors [5]. A typical p-n junction provides about Ϯ10% of linearly varying capacitance, while the recently reported accumulation-mode MOS varactors provide about Ϯ30% [6,7]. With Ϯ30%, the maximum oscillation frequency range is below 40%, and the tuning range can be given by where f max and f min are the maximum and minimum oscillation frequency, and C max and C min are the maximum and minimum capacitance of the varactor, respectively. Thi...

Determination of optimal pumping configuration for an L‐band EDFA with 980‐nm LD and ASE pumps

“…The sensitivity, impedance bandwidth, and radiation patterns of the antenna are considered to be very important design factors in order to achieve efficient communication systems. In addition those factors, the size or volume of the antenna seems to be a critical factor for the embedded antenna [2][3][4]. Although the meander pattern shown in [2] and [4] is particularly useful for reducing the antenna's size, these antennas not only have large size, but also narrow bandwidth for Bluetooth applications.…”

“…One advantage of L-band amplifiers over their C-band counterparts is the inherent gain flatness criteria in which a flat gain profile could be achieved using L-band amplifiers by ensuring that the population inversion in the EDF is around 40% [1] and, therefore, eliminating the need for gainflattening filters. Techniques used to obtain wideband amplification are through parallel or simultaneous gain blocks [2,3], Mach-Zehnder equalizers [4], amplified spontaneous emission (ASE) [5,6], C-band injection [7], as well as reflected pump via fiber Bragg reflectors (FBRs) [8].…”

Gain and noise performances of an L‐band EDFA utilizing a ring laser cavity with fiber Bragg grating

“…C-band EDFAs have a highly structured gain spectrum from 1525 nm to 1565 nm, and therefore require gain equalization to realize a flat-gain spectrum. Similarly, EDFAs having an inherently flat gain spectrum in the L-band (between 1570 -1600 nm) have been realized [1]. Earlier work by Fukushima et al [2] shows gain flatness and noise performance of the L-band EDFA improved by co-pumping with a conventional 1.48-m high-power laser diode in conjunction with an auxiliary 1.55-1.57-m medium-power laser diode.…”

Gain- and noise-figure improvement of a reflective L-band EDFA by using a short length of preamplification EDF

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[2,5]. The advantage of the SA techniques is the ability to provide variations to the CLS method for differing sidelobe topographies.

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