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Detection of fluorescence from a low quantum yield fluorophore is challenging for a fiber-optic probe, especially when an inexpensive and robust construction is desired. We propose a conceptually straightforward theoretical model to optimize the factors affecting the fluorescence-capture capability of a bifurcated/coaxial fiber-optic probe. Experimentally we verify that such a probe, if optimized, can detect the fluorescence of a polymer fluorophore with a low quantum yield of 0.0065.

Based on chirped pulses, a wideband radio frequency (RF) channelized receiver that can easily support hundreds of channels is proposed. The mixing chirped pulses and its own delayed copy produces an equivalent RF local oscillation (LO). The LO frequency can be changed by simply setting the delay between the two paths. Channelized receiving of broadband RF signals can be realized by parallel delay line arrays. Meanwhile, the use of in-phase/quadrature demodulation avoids the extra optical or electrical filtering as well as image interference. A receiver with channel spacing of 100 MHz, covering the spectrum from DC to 18.4 GHz is experimentally demonstrated. The performances, including signal-to-noise ratio, frequency response, spurious-free dynamic range, and image rejection, are analyzed.

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