We report a real-time high-speed fiber Bragg grating (FBG) interrogator based on a fiber-optic interferometer. The signal processing is performed using a low-cost fieldprogrammable gate array (FPGA) system, which is programmed to implement a phase-generated carrier (PGC) demodulation algorithm with multitone mixing (MTM) to provide distortionfree signals with high tolerance to modulation depth variations and light intensity fluctuations. The system can stream data at rates up to 1MS/s and allows multiplexed processing up to two channels. Experimental results show simultaneous measurements of two FBGs, one of which was actuated at frequencies up to 100kHz. The system features a 3-dB bandwidth of 280kHz, and a dynamic wavelength resolution of 4.7 fm/Hz 1/2 . We also demonstrate a strong reduction of distortion using the multitone mixing approach with respect to the standard technique. Finally, we study the origin of the noise, demonstrating a reduction of common noise sources by using one of the FBGs as a reference. The system can measure FBGs centered at any position within the spectral band of the source, is polarization-independent, and is easily scalable to more than two measurement channels from the same interferometer.

We report an interferometer-based multiplexed fiber Bragg grating (FBG) interrogator using silicon photonic technology. The photonic-integrated system includes the grating coupler, active and passive interferometers, a 12-channel wavelength-division-multiplexing (WDM) filter, and Ge photodiodes, all integrated on a 6x8 mm 2 silicon chip. The system also includes optical and electric interfaces to a printed board, which is connected to a real-time electronic board that actively performs the phase demodulation processing using a multitone mixing (MTM) technique. The device with active demodulation, which uses thermally-based phase shifters, features a noise figure of σ = 0.13 pm at a bandwidth of 700 Hz, which corresponds to a dynamic spectral resolution of 4.9 fm/Hz 1/2 . On the other hand, the passive version of the system, based on a 90º-hybrid coupler, features a noise figure of σ = 2.55 pm at a bandwidth of 10 kHz, also showing successful detection of a 42 kHz signal when setting the bandwidth to 50 kHz. These results demonstrate the advantage of integrated photonics, which allows the integration of several systems with different demodulation schemes in the same chip and guarantees easy scalability to a higher number of ports without increasing the dimensions or the cost.

We report FBG interrogation measurements up to 1MS/s using a polarization-maintaining-fiber-based Sagnac interferometer monitored in real time with an FPGA system. The system has lower noise levels than commercial interrogators.

It is well known that interferometers make great sensors. This is because phase is a magnitude that can be measured with very accurate precision and with a great dynamic range at the same time. Integrating these devices on a chip is very appealing because it can make the device much smaller, lighter, and affordable. However, this technology also poses some challenges, which can degrade performance with respect to free-space or fiber-based devices. In this work we overview these challenges and possible strategies to tackle them.

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