Wavelength stabilized 980 nm uncooled pump laser modules for erbium-doped fiber amplifiers

We review the development of wavelength stabilized 980 nm pump laser modules without active temperature stabilization for applications in erbium-doped fiber amplifiers. Operation over a wide temperature range with an output power exceeding 400 mW at an ambient temperature of 70°C is demonstrated. The overall reliability of uncooled modules is estimated to be well below 500 FIT at all operating conditions. Such devices are made possible by continuous development and steady improvement of the pump laser chip, the optimization of the fiber Bragg grating stabilization scheme, careful design of the module package, and extended reliability analysis on the basis of stress tests as well as field data.     

Multiwavelength fiber laser using S-band erbium-doped fiber amplifier and semiconductor optical amplifier

A multiwavelength fiber ring laser that is based on an S-band erbium-doped fiber amplifier (EDFA) and a semiconductor optical amplifier (SOA) is developed. An optical switch is used to switch the multiwavelength fiber laser between S-band and L-band. This fiber laser can stably lase seven wavelengths in the S-band or 28 wavelengths in the L-band. Additionally, the lasing wavelengths with a signal-to-noise ratio of over 33 dB and a wavelength spacing of 100 GHz are demonstrated experimentally. The average powers of the lasing wavelength in the S-band and the L-band are −7.53 and −12.15 dBm, respectively.     

Switchable dual-wavelength polarization-maintaining erbium-doped fiber laser using an optical circulator as the all-reflecting mirror

A simple and effective switchable dual-wavelength polarization-maintaining erbium-doped fiber laser is proposed and demonstrated. Only using a uniform fiber Bragg grating written directly in a segment of the photosensitive and polarization-maintaining erbium-doped fiber as the wavelength selector and an optical circulator as the all-reflecting mirror, a stable simultaneous dual-wavelength oscillation is achieved with a wavelength spacing of 0.364 nm experimentally by exploiting the polarization hole burning effect at room temperature. The output can be switched between single- and dual-wavelength by adjusting the polarization controller. The 3-dB bandwidth and the side mode suppression ratio of the laser’s outputs are measured to be less than 0.01 nm and more than 50 dB. The power fluctuation and wavelength drift are measured to be less than 0.50 dB and 0.020 nm over an hour.     

A global design of an erbium-doped fiber and an erbium-doped fiber amplifier

A global design of an erbium-doped fiber and an open-loop erbium-doped fiber amplifier (EDFA) in a steady-state operation is discussed by applying genetic algorithms. Taking a signal gain and a bandwidth as objective functions, 7 parameters of the EDFA (erbium concentration, core radius, erbium-doped radius, refractive index difference, fiber length, pumping wavelength and signal power) are optimized by solving optical propagation equations, assuming a homogenous two-level active medium and a single-mode propagation. There is evidence to show that the 1480 nm pump utilized in usual EDFAs is not an optimal choice, which should be chosen around 1460 nm. The optimal core radius ranges 0.465–0.548 μm on pumping power 50–200 mW. Under different design objects and with different pumping powers, however, there are different optimal Er-doped concentrations, reflective index differences and fiber lengths. As a single fiber EDFA, 35 dB signal gain or 35 nm bandwidth is obtained with the 7 optimal parameters, 100 mW pumping power and 0.001 mW input signal power.     

A distributed model for continuous-wave erbium-doped fiber laser

A distributed model of a continuous-wave erbium-doped fiber laser is discussed. The model is based on two contra-propagated traveling laser waves, and includes inhomogeneous pumping, excited state absorption at the pump and the laser wavelengths, amplified spontaneous emission and radial distribution of populations of erbium levels. It is shown that excited state absorption is a main limiting factor to the laser's efficiency. Moreover, consideration of radial distributions of erbium levels' populations in the model reduces laser efficiency and decreases optimal reflection of the laser output coupler. The modeling results are in excellent agreement with the experimental study on the EDFL efficiency.     

Switchable triple-wavelength erbium-doped fiber laser using a single fiber Bragg grating in polarization-maintaining fiber

A stable and narrow wavelength spacing multiwavelength erbium-doped fiber laser is proposed and demonstrated. The laser can produce simultaneous dual- and triple-wavelength lasing oscillations with a narrow wavelength spacing of less than 0.1 nm via using a single fiber Bragg gratings written in polarization-maintaining (PM) fiber. By adjusting polarization controller, the wavelength spacing of dual-wavelength lasing oscillations can be tuned to as small as 0.032 nm. The maximum amplitude variation for every lasing wavelength is less than 0.5 dB. The room-temperature operation principle is based on the polarization hole burning and deeply saturated effect in an ordinary erbium-doped fiber ring laser (EDFRL). The laser has the advantages of simple all-fiber configuration, low cost, high stability and operating at room temperature.     

Thermally tunable microfiber knot resonator based erbium-doped fiber laser

A compact and tunable erbium-doped fiber laser is demonstrated using a highly doped fiber and a microfiber knot resonator (MKR) structure which is laid on the surface of a small peltier. The MKR functions as both a reflector and a tunable filter where tunability is achieved by varying the temperature of the resonator by heating the peltier. A stable laser output is achieved at the 1533 nm region with an optical signal to noise ratio (OSNR) of 27 dB using a 65 mW of 980 nm pump power. The operating wavelength of the laser can be tuned from 1532.60 nm to 1533.49 nm as the temperature is increased from the room temperature of 24 to 90 °C. It is observed that the operating wavelength shifts to a longer wavelength as the temperature increases with an efficiency of 12.4 pm/°C. This is due to the thermally induced optical phase shift attributable to the changes in effective refractive index and optical path length of the MKR loop.     

Multiwavelength erbium-doped fiber laser based on nonlinear polarization rotation assisted by four-wave-mixing

We experimentally demonstrate a simple-structure but efficient multiwavelength erbium-doped fiber laser based on nonlinear polarization rotation assisted by four-wave-mixing (FWM). Based on the combination of these two nonlinear mechanisms contributing to intensity-dependent loss to alleviate mode competition, the stable multiwavelength operation at room temperature can be realized in a length of dispersion-shifted fiber. We achieved up to 38-wavelength generation with a spacing of ∼0.4 nm in the laser. In addition, through tuning the birefringence fiber filter, the lasing wavelength can be accurately tuned in the free spectrum range.     

Wavelength-switchable erbium-doped fiber ring laser combined with a Fabry-Perot laser diode and a sampled grating

We present a wavelength-switchable erbium-doped fiber ring laser consisting of an anti-reflection coated Fabry-Perot laser diode (FP-LD) and a sampled fiber Bragg grating (SFBG). The wavelength switching is obtained easily by the shift of FP mode with respect to the reflection peaks of the SFBG. The proposed laser apparatus not only simultaneously emits two wavelengths but also switches between the two wavelengths by adjusting the modes of FP-LD with a change of the injection current of the FP-LD as little as ∼1 mA. The proposed wavelength-switchable erbium-doped fiber ring laser exhibits high laser performance with side-mode suppression ratio (SMSR) ?50 dB.     

百瓦级全光纤结构单频掺铥主振荡功率放大器

报道了平均功率超过百瓦的单频掺铥全光纤结构主振荡功率放大器。使用线宽小于100kHz、中心波长为1.97μm的单频种子源进行级联放大,主放大器的斜率效率为50%。监测放大器的回光功率和光谱,没有发现受激布里渊散射以及其他非线性效应。通过增加泵浦功率,可以获得更高功率的掺铥单频放大输出。     

Switchable dual-wavelength Erbium-doped fiber ring laser with cascaded fiber Bragg gratings

We have experimentally shown wavelength mode switching in a dual-wavelength Erbium-doped single cavity fiber laser where the initial two wavelengths of 1 nm spacing are determined by the cascaded reflection type short-period fiber Bragg gratings having two different centre wavelengths of 1550.5 and 1551.5 nm. The lasing mode depends on the polarization in the ring cavity to migrate from one wavelength to another or operates in both modes in a polarization beam splitter output. To effectively control the polarization in the ring cavity, the polarization controllers were positioned before and after the polarization beam splitter. This method of wavelength switching provides a simple way of mode tuning in dual-wavelength fiber lasers.     

Four-wave mixing self-stability based on photonic crystal fiber and its applications on erbium-doped fiber lasers

The analytic solutions of coupled-mode equations of four-wave mixings (FWMs) are achieved by means of the undepleted approximation and the perturbation method. The self-stability mechanism of the FWM processes is theoretically proved and is applicable to design a new kind of triple-wavelength erbium-doped fiber lasers. The proposed fiber lasers with excellent stability and uniformity are demonstrated by using a flat-near-zero-dispersion high-nonlinear photonic-crystal-fiber. The significant excellence is analyzed in theory and is proved in experiment. Our fiber lasers can stably lase three waves with the power ripple of less than 0.4 dB.     

Multiwavelength erbium-doped fiber laser employing a nonlinear optical loop mirror

A stable and broad bandwidth multiwavelength erbium-doped fiber laser is proposed and demonstrated successfully. A nonlinear optical loop mirror which induces wavelength-dependent cavity loss and behaves as an amplitude equalizer is employed to ensure stable room-temperature multiwavelength operation. Up to 50 wavelengths lasing oscillations with wavelength spacing of 0.8 nm within a 3-dB spectral range of 1562-1605 nm has been achieved. The measured power fluctuation of each wavelength is about 0.1 dB within a 2-h period.     

Double-pass erbium-doped zirconia fiber amplifier for wide-band and flat-gain operations

The double-pass erbium-doped zirconia fiber amplifier (EDZFA) is proposed and demonstrated to provide a wide-band amplification as well as flat-gain operation in both the C- and L-band regions using only a single-gain medium. The proposed amplifier utilizes an erbium-doped zirconia fiber (EDZF) with erbium ion concentration of 2800 ppm as a gain medium. The medium is fabricated in a ternary glass host, zirconia-yttria-aluminum codoped silica fiber through solution doping technique along with modified chemical vapor deposition (MCVD). Compared to a single-pass operation, the double-pass EDZFA shows a better gain performance. At input signal power of 0 dBm and the optimum EDZF length of 2 m, a flat gain of around 16 dB is achieved by the proposed double-pass amplifier with gain variation of approximately 2.5 dB throughout the wavelength range from 1530 to 1590 nm. However, the noise figure of the double-pass amplifier is slightly higher than that of the single-pass due to inefficient population inversion at the input part of the amplifier.     

Switchable multi-wavelength erbium-doped fiber lasers by using cascaded fiber Bragg gratings written in high birefringence fiber

A novel and simple Erbium-doped fiber laser by using cascaded fiber Bragg gratings (FBGs) written in high-birefringence fibers for switchable multi-wavelength operation is proposed. Due to two-peak reflection with orthogonal polarizations of the FBG, the polarization hole-burning effect in the cavity is greatly enhanced. Experimental results show that the stable dual- and three-wavelength lasing operation with very narrow wavelength separation (0.39 nm) can be generated at room temperature. The configuration is simple and flexible. Only by adjusting polarization controllers (PCs), the laser can be switched among the stable single-, dual- and three-wavelength lasing operations.     

Erbium-doped photonic crystal fiber laser with 49 mW

We have demonstrated a continuous-wave (CW) all fiber laser operation at 1558.4 nm of a diode-pumped erbium-doped PCF laser based on 9.6 m erbium-doped PCF. The maximum output power and the threshold of the fiber laser are 49.4 mW and 6.67 mW, respectively. We show that it is possible to achieve a high stability and beam quality laser, which has a great application potential in optical communication field in future.     

Experimental and theoretical studies on a double-pass C-band bismuth-based erbium-doped fiber amplifier

Performance of a Bismuth-based Erbium-doped fiber amplifier is experimentally and theoretically investigated using 1480 nm pumping with double-pass scheme. In the theoretical analysis, the rate and power propagation equations are solved to examine the optimum length for the C-band operation as well as the gain and noise figure characteristics. The calculated small signal gain is 38 dB with gain variation of less than 3 dB. The measured gain is 4 dB lower due to spurious reflections which were ignored in the theoretical analysis. At input signal power of 0 dBm, a gain of 14.5 dB is obtained experimentally with gain variation of less than 1 dB within the wavelength region from 1530 to 1565 nm. The noise figure is less than 12 dB within this region.     

A novel double-Brillouin-frequency spaced multi-wavelength Brillouin erbium-doped fiber laser based on non-linear amplified fiber loop mirror

In the paper, a ring double-Brillouin-frequency spaced multi-wavelength Brillouin erbium-doped fiber laser based on non-linear amplified fiber loop mirror filter is demonstrated, in which the non-linear amplified fiber loop mirror (AFLMF) is used as a filter. At the 980 nm pump power of 10.29 dBm, the tunable laser source center wavelength of 1563 nm and power of −3 dBm, up to 12 even output channels with 0.16 nm spacing are achieved. At the same time, we study the influence of 980 nm pump power, the polarization controller and the tunable laser source center wavelength on the number of Stokes light wave.     

High gain L-band erbium-doped fiber amplifier with two-stage double-pass configuration

An experiment on gain enhancement in the long wavelength band erbium-doped fiber amplifier (L-band EDFA) is demonstrated using dual forward pumping scheme in double-pass system. Compared to a single-stage single-pass scheme, the small signal gain for 1580 nm signal can be improved by 13.5 dB. However, a noise figure penalty of 2.9 dB was obtained due to the backward C-band ASE from second stage and the already amplified signal from the first pass that extracting energy from the forward C-band ASE. The maximum gain improvement of 13.7 dB was obtained at a signal wavelength of 1588 nm while signal and total pump powers were fixed at -30 dBm and 92 mW, respectively.     

Enhancement of pump conversion efficiency in preamplified L-band erbium-doped fiber amplifiers

A new configuration of L-band erbium-doped fiber amplifiers (EDFAs) is presented here. The system contains a double-pass L-band EDFA and an optical preamplifier. Different from conventional preamplified double-pass L-band EDFA systems in which only the forward ASE of the preamplifier is re-used as an auxiliary pump, the new system recycles the backward ASE of the preamplifier as well. Two kinds of main L-band EDFAs are studied, both of which include a section of un-pumped erbium-doped fiber placed in a loop reflector. An improvement of up to 110% in pump conversion efficiency is demonstrated with the proposed recycling of the backward ASE, with respect to the system without recycling.