Identical Fiber Bragg Gratings Research Articles

All-optical flip-flop based on coupled laser diodes

An all-optical set-reset flip-flop is presented that is based on two coupled lasers with separate cavities and lasing at different wavelengths. The lasers are coupled so that lasing in one of the lasers quenches lasing in the other laser. The flip-flop state is determined by the laser that is currently lasing. A rate-equation based model for the flip-flop is developed and used to obtain steady-state characteristics. Important properties of the system, such as the minimum coupling between lasers and the optical power required for switching, are derived from the model. These properties are primarily dependent on the laser mirror reflectivity, the inter-laser coupling, and the power emitted from one of the component lasers, affording the designer great control over the flip-flop properties. The flip-flop is experimentally demonstrated with two lasers constructed from identical semiconductor optical amplifiers (SOAs) and fiber Bragg gratings of different wavelengths. Good agreement between the theory and experiment is obtained. Furthermore, switching over a wide range of input wavelengths is shown; however, increased switching power is required for wavelengths far from the SOA gain peak.

Tunable fiber attenuators for channel power equalization in WDM systems

A tunable fiber attenuator is proposed for channel power equalization in wavelength-division-multiplexed (WDM) optical communication systems. This fiber attenuator consists of two identical fiber Bragg gratings, which are subject to bending in opposite directions by an electrically controlled mechanical driver. The attenuation level at the desired wavelength depends on the amount of bending applied to the gratings. A device with a continuous adjustment of attenuation over a range of 32 dB and a driving voltage of less than 2 V has been demonstrated. The performance of these tunable attenuators for channel power equalization in a two-channel WDM system has been measured. Excellent spectral flattening (+/−0.1 dB) has been achieved for static channel power equalization. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 1–4, 2000.

Tunable fiber attenuators for channel power equalization in WDM systems

A tunable fiber attenuator is proposed for channel power equalization in wavelength-division-multiplexed (WDM) optical communication systems. This fiber attenuator consists of two identical fiber Bragg gratings, which are subject to bending in opposite directions by an electrically controlled mechanical driver. The attenuation level at the desired wavelength depends on the amount of bending applied to the gratings. A device with a continuous adjustment of attenuation over a range of 32 dB and a driving voltage of less than 2 V has been demonstrated. The performance of these tunable attenuators for channel power equalization in a two-channel WDM system has been measured. Excellent spectral flattening (+/−0.1 dB) has been achieved for static channel power equalization. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 1–4, 2000.

Pressure vessel wall thinning detection using multiple pairs of fiber Bragg gratings for unbalanced strain measurements

This paper proposes a method for using a pair of identical fiber Bragg gratings to measure the unbalanced strain factor in an isothermal-mechanical system. Cascading two identical fiber Bragg gratings, the unbalanced strain factor caused by the disturbance can be interrogated from the peak difference of the two reflecting Bragg wavelengths. If the mechanical system is in an isothermal environment, the thermal variations in the Bragg grating detection system can be automatically compensated. To verify the feasibility of the unbalanced strain detection using a pair of fiber Bragg gratings, the wall-thinning monitor in a pressure vessel system was investigated. The proposed technique is easy to install, immune to electro-magnetic and thermal interference, and highly sensitive in-time to remote monitoring for fiber optic smart structures. A finite element model (FEM) is used to simulate the wall thinning in a pressure vessel system. The minimum detectable unbalanced strain and cross-talk between two reflecting Bragg wavelengths were investigated.

Channel-switching active add/drop multiplexer withtunable gratings

The authors propose and experimentally demonstrate a novel channel-switching active add/drop multiplexer. Using four identical tunable fibre Bragg gratings, together with the wavelength-overlapping technique, they have constructed an add/drop multiplexer which offers 15 different configurations of drop channels.

Referencing technique for intensity-basedsensors using fibre optic Bragg gratings

An all-optical fibre referencing scheme for intensity based sensors which uses two identical fibre Bragg gratings is described. It provides a general and simple miniature sensor design with referencing effectiveness against system power fluctuations. The concept is demonstrated for a reflective-type displacement sensing cavity, and its potential for simultaneous measurand and temperature evaluation is evaluated.