J. M. Estudillo-Ayala

Widely tunable erbium-doped fiber laser based on multimode interference effect

A widely tunable erbium-doped all-fiber laser has been demonstrated. The tunable mechanism is based on a novel tunable filter using multimode interference effects (MMI). The tunable MMI filter was applied to fabricate a tunable erbium-doped fiber laser via a standard ring cavity. A tuning range of 60 nm was obtained, ranging from 1549 nm to 1609 nm, with a signal to noise ratio of 40 dB. The tunable MMI filter mechanism is very simple and inexpensive, but also quite efficient as a wavelength tunable filter.

Supercontinuum generation in a standard fiber pumped by noise-like pulses from a figure-eight fiber laser

We report the experimental study of broadband spectrum generation in a piece of standard fiber (SMF-28) using as the pump a train of noise-like pulses, or sub-nanosecond packets of sub-ps pulses with randomly varying amplitudes. The pulses are generated by an erbium-doped figure-eight fiber laser, and present a wide (∼50 nm) optical spectrum, which represents a significant advantage to seed the generation of new frequencies. Another advantage of the pulses is their relatively large energy, as they are made up of a large number of ultrashort pulses. After amplification with an Erbium Doped Fiber Amplifier (EDFA), the pulses were injected in a 0.75 km length of SMF-28 fiber. We obtained experimentally at the end of the fiber an output signal spectrum extending from 1530 nm to at least 1750 nm (the upper limit of the spectrum analyzer) for pump pulses with an average power of 20.4 mW, corresponding to a few kilowatts peak power. The spectral broadening is due to Raman self-frequency shift (SFS). It is noteworthy that the spectrum of the newly created frequencies was extremely uniform over the range of measurement. Considering that the Raman shift is directly related to the pump pulse duration, spectral flatness is a direct consequence of the random distribution of amplitudes and durations of the pulses in the packet. Finally, the results show the capabilities of noise-like pulses from a fiber laser for applications in supercontinuum generation based on nonlinear phenomena such as Raman SFS.

Laser Temperature Sensor Based on a Fiber Bragg Grating

In this letter, a temperature sensor based on a fiber ring laser is presented. A fiber Bragg grating was used as a sensor head, and a Mach-Zehnder interferometer (MZI) was utilized as a wavelength selective filter to enhance the temperature sensing capability. The MZI was achieved by splicing a piece of photonic crystal fiber between two segments of single-mode fiber. Moreover, it is shown that when the laser emission wavelength is shifted as the temperature is varied, achieving a temperature sensitivity of 18.8 pm/°C at 1550 nm, within the temperature range from 20 °C to 90 °C.

An All Fiber Intrinsic Fabry-Perot Interferometer Based on an Air-Microcavity

In this work an Intrinsic Fabry-Perot Interferometer (IFPI) based on an air-microcavity is presented. Here the air microcavity, with silica walls, is formed at a segment of a hollow core photonic crystal fiber (HCPCF), which is fusion spliced with a single mode fiber (SMF). Moreover, the spectral response of the IFPI is experimentally characterized and some results are provided. Finally, the viability to use the IFPI to implement a simple, compact size, and low cost refractive index sensor is briefly analyzed.

A tunable multi-wavelength laser based on a Mach?Zehnder interferometer with photonic crystal fiber

In this paper a tunable multi-wavelength erbium doped fiber laser, based on a Mach–Zehnder interferometer, is presented. Here the interferometer is achieved by splicing a piece of photonic crystal fiber (PCF) between two segments of a single-mode fiber. The laser can emit a single, double, triple or quadruple line, which can be tuned from 1530 to 1556 nm by controlling the polarization state. Finally it is shown, by experimental results, that the laser has high stability at room temperature.

All-Fiber Curvature Sensor Based on an Abrupt Tapered Fiber and a Fabry–Pérot Interferometer

In this letter, a highly sensitive curvature sensor arrangement based on an abrupt tapered fiber (ATF) concatenated with an all-fiber micro Fabry-Pérot interferometer (MFPI) is presented. Here, as the ATF is bent, the MFPI spectral fringes contrast decreases. In addition, the curvature sensitivity is considerably enhanced due to the use of the ATF. Finally, it is shown that with this arrangement, at 1530-nm wavelength, it is possible to detect curvature changes with a sensitivity of 11.27 dB/m-1 and a curvature resolution of 8.87 × 10-3 m-1 within the measurement range of 0 - 3.5 m-1.

A tunable multi-wavelength erbium doped fiber laser based on a Mach–Zehnder interferometer and photonic crystal fiber

In this paper a tunable multi-wavelength erbium doped fiber laser, based on a Mach–Zehnder interferometer, is presented. The interferometer is achieved by splicing a piece of photonic crystal fiber between two segments of a single-mode fiber. Here, by changing the curvature radius in the Mach–Zehnder interferometer, the single-, double- or triple-line emissions can be tuned from 1526 to 1550 nm. Finally it is shown, via experimental results, that the laser has high stability at room temperature.

Measurement of beat length in short low-birefringence fibers using the fiber optical loop mirror

Abstract In this paper we provide a detailed analysis and investigation of a novel experimental method to measure the birefringence in short low-birefringence fibers. This method is based on the fiber’s twist in a fiber optical loop mirror. It allows simple birefringence measurement in fibers with beat length within the range of 0.4–100 m. The shortest fiber we were able to measure was 0.034 of beat length. Statistical error of measurements was less than 3%. To demonstrate the measurement technique we present experimental results for three optical fibers whose beat lengths were in the range from 1 to 19 m.

A Core-Offset Mach Zehnder Interferometer Based on A Non-Zero Dispersion-Shifted Fiber and Its Torsion Sensing Application

In this paper, an all-fiber Mach-Zehnder interferometer (MZI) based on a non-zero dispersion-shifted fiber (NZ-DSF) is presented. The MZI was implemented by core-offset fusion splicing one section of a NZ-DSF fiber between two pieces of single mode fibers (SMFs). Here, the NZ-DSF core and cladding were used as the arms of the MZI, while the core-offset sections acted as optical fiber couplers. Thus, a MZI interference spectrum with a fringe contrast (FC) of about 20 dB was observed. Moreover, its response spectrum was experimentally characterized to the torsion parameter and a sensitivity of 0.070 nm/° was achieved. Finally, these MZIs can be implemented in a compact size and low cost.

Experimental study on a broad and flat supercontinuum spectrum generated through a system of two PCFs

In this letter, the experimental results on a supercontinuum signal are presented based on a significantly broad and highly flat final spectrum (~810 nm and less than 3 dB). The supercontinuum was induced by two different microstructures in photonic crystal fibers (PCFs) with solid cores, pumped in the nanosecond regime (large pulses) by a Q-switched Nd:YAG laser. The simultaneous presence of both PCFs allowed an optimized spectrum to be obtained in comparison with the work reported in recent papers. The spectral evolution of a pump pulse propagating into the two PCFs was analyzed experimentally and the dispersion in the PCFs was estimated through numerical simulations. The broadening of the final spectrum was related to nonlinear phenomena such as modulation instability, stimulated Raman scattering, four-wave mixing, self-phase modulation, cross-phase modulation and the formation of higher-order solitons. The proposed scheme may have potential applications for the use of supercontinuum spectra in the areas of sensing, spectroscopy and metrology.