In this paper we report a fiber-type widely tunable CW mid-IR DFG/QPM laser source based on periodically poled MgO-doped LiNbO3 (PPMgLN), which uses a ytterbium-dope fiber laser (YDFL) as the pump source and a tunable erbium-dope fiber laser (EDFL) cascaded with an erbium-doped fiber amplifier (EDFA) as the signal source. Our experimental results show that, with the PCs to adjust the pump and signal polarization orientations being parallel to the crystal principle optical axis the conversion efficiency may be optimized. The pump and signal beam spots and their longitudinal evolution behaviors determine the RCE and the crystal longitudinal position tolerance, which are measured to be 0.717 (mW)-2 and 44 mm for the mid-IR laser source, respectively. The idler output of the mid-IR DFG/QPM laser source may be continuously tuned from 3.1 to 3.6 μm with almost the same RCE.

Widely tunable continuous wave mid-IR DFG source based on fiber lasers and amplifiers

An analytically expression for the temperature dependence of the signal gain of an erbium-doped fiber amplifier (EDFA) pumped at 1480 nm are theoretically obtained by solving the propagation equations with the amplified spontaneous emission (ASE). It is seen that the temperature dependence of the gain strongly depends on the distribution of population of Er3+-ions in the second level. In addition, the output pump power and the intrinsic saturation power of the signal beam are obtained as a function of the temperature. Numerical calculations are carried out for the temperature range from -20 to +60 °C and the various fiber lengths. But the other gain parameters, such as the pump and signal wavelengths and their powers, are taken as constants. It is shown that the gain decreases with increasing temperature within the range of L≤27 m.

The temperature dependent performance analysis of EDFAs pumped at 1480 nm: A more accurate propagation equation

An investigation on the temperature dependence of the relative population inversion and the gain in EDFAs by the modified rate equations

Extending the sensing range for monitoring the railways, pipelines, borders, long structures, etc., has great importance in distributed fiber optic sensors development. Phase-sensitive optical time-domain reflectometry (φ-OTDR) sensors are the best candidate for this purpose. Optical fiber amplifiers in φ-OTDR sensors have increased the sensing range. A φ-OTDR sensor using combination of Erbium and Raman amplifiers has been demonstrated with a sensing range of 128 km. In this paper, we presented a disturbance monitoring up to 150 km utilizing Erbium and bi-directional Raman amplifications. In the proposed sensor, disturbances at 30, 70 and 120 km distances are applied and Rayleigh backscattered signals are investigated.

150 km φ-OTDR sensor based on erbium and Raman amplifiers

A mid-IR multiwavelength difference frequency generation (DFG) laser source with fiber laser fundamental lights is demonstrated by using the dispersion property of PPLN to broaden the quasi-phase-matching (QPM) acceptance bandwidth (BW). Our results show that the QPM BW for the pump YDFL is much larger than that for the signal EDFL. Using a multiwavelength YDFL and a single-wavelength EDFL as the pump and the signal lights, the DFG laser source can simultaneously emit 14 mid-IR wavelengths with the spacing of 14 nm at a fixed PPLN temperature. Moreover, mid-IR multiwavelength lasing lines can be synchronously tuned between 3.28 and 3.47 microm.

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Jingsong Wang

Papers

A theoretical analysis of amplification characteristics of bi-directional erbium-doped fiber amplifiers with single erbium-doped fiber

Experimental Study on Mechanical Properties of Concrete Canvas and Cfrp Joint Confined Concrete Columns Under Axial Comperssion