We report the first compact silicon CMOS 1x4 tunable multiplexer/ demultiplexer using cascaded silicon photonic ring-resonator based add/drop filters with a radius of 12 microm, and integrated doped-resistor thermal tuners. We measured an insertion loss of less than 1 dB, a channel isolation of better than 16 dB for a channel spacing of 200 GHz, and a uniform 3 dB pass band larger than 0.4 nm across all four channels. We demonstrated accurate channel alignment to WDM ITU grid wavelengths using integrated silicon heaters with a tuning efficiency of 90 pm/mW. Using this device in a 10 Gbps data link, we observed a low power penalty of 0.6 dB.

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The next generation of gas turbine engines will potentially have Full Authority Digital Eengine Control (FADEC) Systems that consists of wired, wireless, and fiber optics technologies. This paper focuses on the fiber optics technologies for engine applications. Optical fiber sensors have the potential to deliver new and effective measurement in many applications aided by the following properties: (a) immunity to and non-generation of electromagnetic interference (EMI), (b) electrical passivity and thus safety in explosive environments, (c) transmission of sensed information over long distances and through difficult to access regions, (d) very small diameter size allowing integration into smart materials, (d) high durability in many environments, (e) minimal mass, particularly important in aerospace applications, (f) geometric flexibility coupled with capability for multiple functionality, enabling "non-line-of-sight" measurements and contributing to ease of installation compared with alternative approaches. For practical application a fiber optic sensing system needs to include: sensors, fiber optic link, interrogator (comprising photonics, electronics and firmware/software), data interpretation and decision-aid algorithms/software. Fiber optics for diagnostics and troubleshooting are used in varying capacities to test, measure, analyze, transmit, distribute, and/or simulate an optical signal with which procedures and processes associated with maintenance, problem solving, and calibration of equipment and/or networks can be performed. With all the scientific and engineering advancements in the field of fiber optic sensing, the maturity of this technology is high enough and well beyond the experimental lab environment. With its rather low cost, fiber optics sensing technology is a proper option for turbine engine industry.

Electromechanical impedance is a popular diagnostic method for assessing structural conditions at high frequencies. It has been utilized, and shown utility, in aeronautic, space, naval, civil, mechanical, and other types of structures. By contrast, fiber optic sensing initially found its niche in static strain measurement and low frequency structural dynamic testing. Any low frequency limitations of the fiber optic sensing, however, are mainly governed by its hardware elements. As hardware improves, so does the bandwidth (frequency range * number of sensors) provided by the appropriate enabling fiber optic sensor interrogation system. In this contribution we demonstrate simultaneous high frequency measurements using fiber optic and electromechanical impedance structural health monitoring technologies.A laboratory specimen imitating an aircraft wing structure, incorporating surfaces with adjustable boundary conditions, was instrumented with piezoelectric and fiber optic sensors. Experiments were conducted at different structural boundary conditions associated with deterioration of structural health. High frequency dynamic responses were collected at multiple locations on a laboratory wing specimen and conclusions were drawn about correspondence between structural damage and dynamic signatures as well as correlation between electromechanical impedance and fiber optic sensors spectra. Theoretical investigation of the effect of boundary conditions on electromechanical impedance spectra is presented and connection to low frequency structural dynamics is suggested. It is envisioned that acquisition of high frequency structural dynamic responses with multiple fiber optic sensors may open new diagnostic capabilities for fiber optic sensing technologies.

Structural dynamic characterization is important for ensuring reliability and operability of spacecraft payloads in harsh environments. During the launch, a structure experiences dynamic loads, including acoustic excitation. Conventional sensors are used to infer structural dynamic characteristics. Limitations of conventional strain sensors include low frequency band, susceptibility to electro-magnetic interference, and use of multiple wires. To mitigate these deficiencies, an innovative fiber optic strain measurement system is considered to obtain strain distribution at specific locations on a payload. Theoretical models are suggested and compared with results of experimental testing. Limitations of analytical models are discussed and comparisons with numerical models are presented. The research addresses the usability of presented models in determining the dynamic response of a payload and variation due to distribution of components. It is proposed that discussed experimental and theoretical procedures can be used in determining structural performance for a variety of missions. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 08/17/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Proc. of SPIE Vol. 8695 869511-2 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 08/17/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx Proc. of SPIE Vol. 8695 869511-8 Downloaded From: http://proceedings.spiedigitallibrary.org/ on 08/17/2015 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx