Wencai Huang

Stable and wideband L-band erbium superfluorescent fiber source using improved bidirectional pumping configuration

We have proposed and demonstrated a wideband and wavelength stable L-band erbium-doped superfluorescent fiber source (SFS) using an improved double-pass bi-directional (DP-BD) pumping configuration with a segment of un-pumped fiber. The effects of the fiber length and pump power arrangements on the output characteristics of the L-band SFS are examined. Simulations and experiments show that the output characteristics of the L-band SFS are significantly improved by using an un-pumped fiber in the DP-BD pumping configuration. This designed configuration allows a wavelength stable L-band SFS operation with a broadening bandwidth of 52.6nm, an enhanced pumping efficiency of 47.5%, and a mean wavelength of 1580.42nm.

A pump power insensitive high stability L-band erbium-doped superfluorescent fibre source

A simple one-stage configuration for a high stability L-band (1565?1605?nm) erbium-doped superfluorescent fibre source (SFS) is designed and investigated for the first time. The SFS is realized in a section of erbium-doped fibre (EDF) with a double-pass bi-directional pump configuration. With an appropriate pump ratio of forward to total pump power and fibre length, pump power insensitive mean wavelength L-band SFS operation can be obtained. Theoretical simulations indicate that the proportion of the forward pump power to the total pump power should be 0.2, in order to obtain high mean wavelength stability and high output power simultaneously. For a 19?m long EDF with a peak absorption of 27?33?dB?m?1 at 1530?nm, a SFS with a linewidth of 42.6?nm, an output power of 34?mW, and a high mean wavelength stability insensitive to pump power is obtained with a pump ratio of 0.2 and 82?mW total pump power. Pump power insensitive mean wavelength characteristics are attributable to the bi-directional pumping configuration and the use of a power splitter which ensures simultaneous variations of forward and backward pump power.

A novel super-high extinction ratio comb-filter based on cascaded Mach-Zehnder Gires-Tournois interferometers with dispersion compensation

In this paper, we propose a novel Mach-Zehnder Gires- Tournois interferometer (MZGTI) and a scheme to realize super high extinction ratio flat-top comb filter based on cascaded MZGTIs. Two sets of novel multi-cavity transmissive Gires-Tournois etalon (MCT-GTE) composed of cascaded Mach-Zehnder interferometer loops are added to the two arms of Mach-Zehnder interferometer (MZI) respectively, which forms a new MZI, i.e., MZGTI. MZGTI has the same characteristics as Michelson-Gires-Tournois interferometer (MGTI), which is suitable for dense wavelength division multiplexing systems. The super-high extinction ratio comb filter (SHERCF) we proposed has good passband flatness and wide bandwidth (passband or stopband bandwidth) when the extinction ratio is fairly high, which is quite superior to MGTI or MZGTI. For the severe chromatic dispersion problems, we propose a set of multi-cavity ring resonator (MC-RR) as a tunable dispersion compensator (TDC) for MZGTI, which is a set of cascaded ring resonators. Moreover, we demonstrate that a set of cascaded MC-RRs is an efficient dispersion compensator for SHERCF with the optimized results.

Low-ripple and high-efficiency C+L-band erbium-doped fiber amplified-spontaneous-emission sources using a dual forward pumping configuration

We have experimentally investigated a new two-stage C+L-band (1525 to 1605-nm) amplified spontaneous emission (ASE) fiber source using a dual forward pumping configuration. The proposed source offers a high pumping efficiency of 24.6%, output power of about 52 mW, and a wide bandwidth of 80 nm. Without using any external spectral filters, the source has a low spectral ripple between 2.4 and 2.9 dB for different pumping power levels. This designed configuration is also suitable for high-efficiency L-band ASE. The obtained source will be useful in characteristic measurement for wavelength-division multiplexing components and spectrum-sliced multiwavelength fiber sources for local access networks.

A C+L-band erbium-doped fiber ASE source using dual-forward pumping configuration

We present a C+L-band ASE fiber source using double-pass dual-forward pumping configuration. The proposed ASE source offers a high pumping efficiency of 24.6%, output power of 52 mW and a wide bandwidth of about 80 nm.

Application of Lambert W function to Raman fiber laser

With the assistance of Lambert W function, we derive an explicit expression for output power of Raman fiber laser without using the depleted-pump approximation. Moreover, the optimal fiber length and FBG reflectivity are obtained analytically.

Band selective C− or C+L-band ASE source using the backward feedback technique

We present a C− or C+L-band selective ASE source using the 1×2 optical switch in a bi-directional pumping configuration. The 25.9mW C-band or 22.5mW C+L-band ASE spectrum is obtained merely by control the state of the optical switch.

High pumping-efficiency and wideband L-band erbium-doped fiber ASE source using two-stage double-pass backward pumping configuration

We present a wideband and high pumping-efficiency L-band erbium-doped fiber (EDF) amplified spontaneous emission (ASE) source using a two-stage double pass backward (DPB) pumping configuration.DPB configuration has been proved to have a high pumping-efficiency. In this paper we use a two-stage DPB pumping configuration to generate a stable L-band ASE source for the first time. The source consists of two sections of EDF, a 1480nm pumping laser diode (LD) which is divided into two portions to pump two sections of EDF separately. By using a power splitter, the pumping power of two stages can be adjusted proportionally. The effects of EDF length and pump power arrangement on the output characteristics of L-band ASE spectrum, output power and mean wavelength are theoretically investigated. The results show that the pumping-conversion efficiency and the linewidth can be improved significantly by optimizing the fiber length ratio and pump ratio of the two-stage DPB configuration. Based on former work, the total fiber length is chosen at 19m in this paper. With the total fiber length fixed, the proposed source has a high pumping efficiency of 53%, an output power of 111mW, and a broadening linewidth of 49nm with the mean wavelength at 1580.18nm under the optimizing fiber ratio of 0.842 and pump power ratio of 0.5.

High power LD-end-pumped Nd:YVO4 laser as a pump source for raman fiber laser

A LD-single-end-pumped Nd:YVO4 CW all-solid-state laser with maximum output power 12.5W at 1064nm was designed to pump the cascaded phosphosilicate fiber Raman laser. The Nd:YVO4 laser is lower in cost than Yb-doped cladding fiber laser which is usually used as a pump for Raman fiber laser. However, it is inefficient to couple pump beam into single mode fiber (SMF). The coupling efficiency from pump beam to SMF is largely affected by the beam quality. Thus, a high coupling efficiency requires maintaining lasers operation in the TEM00 mode while scaling the power. The beam quality and maximum output power of the Nd:YVO4 laser is restricted by the thermal lens and fracture within the gain medium under high pump intensity conditions. The thermal effects was decreased by using a 3×3× 10mm3 Nd:YVO4 crystal with a low neodymium-doped concentration (0.3at%). Furthermore, a plane-plane resonant cavity with large mode volume and a large pump size was also used to reduce the effects. The Nd:YVO4 laser with maximum output power 12.5W and M2<1.2 was obtained. More power than 4W was injected into cascaded Raman cavity at the maximum pump power and about 1W coherent second-order Stokes radiation at 1484nm was achieved.

Design optimization of the first-order P-doped fiber Raman lasers using an explicit approach

Theoretical design optimization of the first-order P-doped fiber Raman laser (FRL) by an explicit approach was investigated. The authors derived an explicit expression for the output power of the laser without using the depleted-pump approximation. The proposed solution shows excellent agreement with numerical simulation. According to the explicit solution, one can clearly know the effects of fiber length, reflectivity of output fiber Bragg grating (FBG), Raman gain and loss of the P-doped fiber and extra losses on the output power. The solution also present a criteria by which one can determine whether the depleted-pump approximation is valid or not. It is very fast and convenient to optimize the output power of the FRL using the proposed explicit solution. The optimal values of fiber length, reflectivity of output FBG and conversion efficiency are obtained under different pump power. While increasing pump power, the optimal fiber length and reflectivity of output FBG decrease and the optimal conversion efficiency increase. There exists a certain tolerance of the optimal parameters, in which the conversion efficiency decreases only slightly. The results provide us an intuitive physical understanding to the laser and are instructive to experimental design of the laser.