This paper describes the design and performance of a new all optical fiber-coupled Fabry-Perot (FP) acceleration and vibration sensor. This device can be readily multiplexed with up to eight other sensors on a single interrogation channel, and an existing state of the art Fiber Bragg Grating (FBG) swept-wavelength interrogation system can be used to monitor the sensor response. The ease of multiplexing combined with passive operation leads to an effective solution for monitoring vibration at many different points across a wide area, with minimal cost of deployment. We will also describe tests of a fiber conduit security monitoring application.
Optical coherence tomography (OCT) has become a useful and common diagnostic tool within the field of ophthalmology. Although presently a commercial technology, research continues in improving image quality and applying the imaging method to other tissue types. Swept-wavelength lasers based upon fiber ring cavities containing fiber Fabry-P´erot tunable filters (FFP-TF), as an intracavity element, provide swept-source optical coherence tomography (SS-OCT) systems with a robust and scalable platform. The FFP-TF can be fabricated within a large range of operating wavelengths, free spectral ranges (FSR), and finesses. To date, FFP-TFs have been fabricated at operating wavelengths from 400 nm to 2.2 µm, FSRs as large as 45 THz, and finesses as high as 30 000. The results in this paper focus on presenting the capability of the FFP-TF as an intracavity element in producing swept-wavelength lasers sources and quantifying the trade off between coherence length and sweep range. We present results within a range of feasible operating conditions. Particular focus is given to the discovery of laser configurations that result in maximization of sweep range and/or power. A novel approach to the electronic drive of the PZT-based FFP-TF is also presented, which eliminates the need for the existence of a mechanical resonance of the optical device. This approach substantially increases the range of drive frequencies with which the filter can be driven and has a positive impact for both the short all-fiber laser cavity (presented in this paper) and long cavity FDML designs as well.
This paper discusses the use of laterally deformable optical nanoelectromechanical systems (NEMS) grating transducers for sensor applications. For very small changes in the spacing of the nanostructured grating elements, a large change in the optical reflection amplitude is observed, making this an ideal transducer element for detecting very small amounts of relative motion. These devices are also very sensitive to wavelength, and could thus be used as tunable elements for spectrometry, as well as communications or inertial sensing. This anomalous diffraction property was predicted in previous work; here, we experimentally verify operation of these devices and demonstrate a motion detection sensitivity of 10 fm/Hz<sup>1/2</sup>, comparable to the most sensitive MEMS transducer. As optical devices, these sensors have additional advantages over electrical sensors, including high immunity to electromagnetic interference and the possibility of integration with fiber optics to create a network of sensors with a single remote optical source and detector.
We have experimentally demonstrated operation of a laterally deformable optical NEMS grating transducer. The device is fabricated in amorphous diamond on a silicon substrate with standard lithographic techniques. For small changes in the spacing of the grating elements, a large change in the optical reflection amplitude is observed. An in-plane motion detection sensitivity of 160 fm/√Hz has been measured, which agrees well with theoretical models. This sensitivity compares favorably to that of any other MEMS transducer. Calculations predict that this sensitivity could be improved by up to two orders of magnitude in future designs. As well as having applications to the field of accelerometers and other inertial sensors, this device could also be used as a modulator for optical switching.
Conference Committee Involvement (2)
Nanofabrication: Technologies, Devices, and Applications II
23 October 2005 | Boston, MA, United States
Nanofabrication: Technologies, Devices, and Applications
25 October 2004 | Philadelphia, Pennsylvania, United States