M. A. G. Martinez

Numerical simulations and experimental results of a hybrid EDFA-Raman amplifier

In this work numerical simulated and experimental results are obtained for a hybrid EDFA-Raman amplifier. Rigorous numerical models of both EDFA and Raman amplifiers are implemented and validated with experimental measurements. Results of ripple smaller than 1 dB are obtained for the hybrid amplifier gain, in 40 nm of bandwidth. The numerical model permits to achieve optimal design and to predict flat amplifier gain using genetic algorithm.

Fabrication of a spun elliptically birefringent photonic crystal fiber and its characterization as an electrical current sensor

In this paper a spun elliptically birefringent photonic crystal fiber is fabricated and characterized. Its performance as a current sensor, using a polarimetric configuration, was tested and compared against single mode fiber at 633 nm. In particular the sensor sensitivity and linearity was investigated using fiber loops with different radius or number of turns around the conductor. The results obtained show that the spun fiber (40 rotation per meter) is able to suppress quite effectively the effects of the bend induced birefringence as compared to the standard fiber.

Brillouin effects in distributed Raman amplifiers under saturated conditions

This paper analyzes experimentally the limitations observed in lightwave systems using distributed Raman amplifiers operating under large pump power input conditions. The Brillouin effect is observed as the pump power becomes equal to 1 watt centered in a specific pump wavelength. The presence of Brillouin peaks degrades the system performance. The Raman amplifier is set with singlemode and dispersion compensating fibers and evaluated in a high capacity WDM link at transmission rates up to 40 Gb/s per channel. The dispersion compensation was accomplished by adjusting the length of the dispersion compensating fiber. The system and amplifier characterization were developed in terms of the on-off gain, ripple, optical signal-to-noise ratio, eye diagram and extinction ratio.

Long-Period Gratings Dynamic Interrogation With Modulated Fiber Bragg Gratings and Optical Amplification

It is reported a long-period grating (LPG) dynamic interrogation technique based on the modulation of fiber Bragg gratings located in the readout unit of the system. It permits to attenuate the effect of the noise of the electronics in the resolution of the LPG-based sensing head. The concept is tested to detect variations of the external refractive index and a resolution of 2.010 NIR was achieved without system optimization. Additionally, the effect in the sensor resolution when introducing Erbium and Raman optical amplification is experimentally investigated.

Dynamic interrogation of long period gratings with modulated fibre Bragg gratings

It is reported a LPG dynamic interrogation technique based on the modulation of fibre Bragg gratings located in the readout unit that permits to attenuate the effect of the 1/f noise of the electronics in the resolution of the LPG-based sensing head. The concept is tested to detect variations of the external refractive index and a resolution of 2.0×10-4 NIR was achieved without system optimization. Additionally, the effect in the sensor resolution when introducing Erbium and Raman optical amplification is experimentally investigated.

A study of the quantitative impact of pump-pump interaction in wide-band Raman amplifiers in the S, C and L bands

A quantitative study on the impact of pump-pump interaction in wide band Raman amplifiers in the S, C and L bands is reported here. For this purpose, the nonlinear coupled Raman equations are written in a novel format separating the different mechanisms which contribute to gain profile, among them, pump-pump interaction. The study is applied to a modern low loss fiber under three pump excitation. The minimum total pump power required to pump-pump interaction mechanisms is investigated for the co and couter propagating amplifier configuration. These threshold power level is significantly different for both configurations. In the co propagating configuration it is independent on the amplifier length while for the counter propagating configuration it is dependent on the amplifier length. to affect gain profile is dependent on fiber length for the counter propagation amplifier configuration while it is independent on fiber length for the co-propagating configuration. Further, a sensitivity analysis of gain flatness as a function of the central pump wavelength power is conduction for both amplifier configurations. The counter propagation configuration is less sensitive to center wavelength power level variation when compared to the co propagating configuration.

Fabrication and characterization of spun HiBi PCF fibers for current sensing applications

In this paper three highly birefringent (HiBi) spun photonic crystal fibers (PCF) are fabricated and their performance are characterized for electrical current measurement. These fibers are tested by coiling them around an electric conductor using three distinct winding diameters with different turns. The results present a very good linear relation with the current and its sensitivity depends on the winding diameter and on the number of turns. For the larger winding diameter, the fiber with lower circular pitch had higher sensitivity and for the smaller winding diameter the best sensitivity result was for the fiber with higher circular pitch.

Development of an electrical current sensor prototype for applications in high-power lines

A magneto-optical current sensor, based on a low birefringence SF57 glass prism, using a dual quadrature polarimetric configuration was implemented and tested aiming its application in high voltage power lines. Sensor operation is characterized and compared using distinct Super Luminescent Diodes as optical sources, with emission at 650 nm, 830 nm and 1550 nm. Calibration and resolution are obtained in the different operating conditions using a DAQ board and full digital control for signal acquisition and processing. In particular, the sensor was tested in the range from 0 to 1 kA at 50 Hz. Also, operation at different frequencies from 50 Hz to 400 Hz was compared. A robust casing was fabricated in Nylon material enabling the portability of the sensor and its application in different types of conductors. Preliminary results indicate the feasibility of using the sensor both for metering and protection applications in high-power lines with interrogation via the OPGW cable.

An approach to analyze quantitavily pump-pump interaction in Raman amplifiers

We report a simple and straightforward approach to analyze quantitatively pump-pump interaction contribution to wide-band Raman amplifier gain profile. The approach is based in the numerical solution of Raman amplification equations. The on-off gain difference in the presence and absence of pump-pump interaction depicts a degree of odd symmetry in gain profile around the center of the amplification band. Additionally, the approach evidences a pump power threshold level where pump-pump interaction plays a relevant role in gain profile. The approach is demonstrated for modern low loss fibers under three and two pump excitation.