865 research outputs found
Tunable Fiber Bragg Grating Ring Lasers using Macro Fiber Composite Actuators
The research reported herein includes the fabrication of a tunable optical fiber Bragg grating (FBG) fiber ring laser (FRL)1 from commercially available components as a high-speed alternative tunable laser source for NASA Langley s optical frequency domain reflectometer (OFDR) interrogator, which reads low reflectivity FBG sensors. A Macro-Fiber Composite (MFC) actuator invented at NASA Langley Research Center (LaRC) was selected to tune the laser. MFC actuators use a piezoelectric sheet cut into uniaxially aligned rectangular piezo-fibers surrounded by a polymer matrix and incorporate interdigitated electrodes to deliver electric fields along the length of the piezo-fibers. This configuration enables MFC actuators to produce displacements larger than the original uncut piezoelectric sheet. The FBG filter was sandwiched between two MFC actuators, and when strained, produced approximately 3.62 nm of wavelength shift in the FRL when biasing the MFC actuators from 500 V to 2000 V. This tunability range is comparable to that of other tunable lasers and is adequate for interrogating FBG sensors using OFDR technology. Three different FRL configurations were studied. Configuration A examined the importance of erbium-doped fiber length and output coupling. Configuration B demonstrated the importance of the FBG filter. Configuration C added an output coupler to increase the output power and to isolate the filter. Only configuration C was tuned because it offered the best optical power output of the three configurations. Use of Plastic Optical Fiber (POF) FBG s holds promise for enhanced tunability in future research
Wideband tunable microwave signal generation in a silicon-based optoelectronic oscillator
Si photonics has an immense potential for the development of compact and
low-loss opto-electronic oscillators (OEO), with applications in radar and
wireless communications. However, current Si OEO have shown a limited
performance. Si OEO relying on direct conversion of intensity modulated signals
into the microwave domain yield a limited tunability. Wider tunability has been
shown by indirect phase-modulation to intensity-modulation conversion,
requiring precise control of the phase-modulation. Here, we propose a new
approach enabling Si OEOs with wide tunability and direct intensity-modulation
to microwave conversion. The microwave signal is created by the beating between
an optical source and single sideband modulation signal, selected by an
add-drop ring resonator working as an optical bandpass filter. The tunability
is achieved by changing the wavelength spacing between the optical source and
resonance peak of the resonator. Based on this concept, we experimentally
demonstrate microwave signal generation between 6 GHz and 18 GHz, the widest
range for a Si-based OEO. Moreover, preliminary results indicate that the
proposed Si OEO provides precise refractive index monitoring, with a
sensitivity of 94350 GHz RIU and a potential limit of detection of only 10-8
RIU, opening a new route for the implementation of high-performance Si photonic
sensors
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