Figure 2
From: High fidelity fibre-based physiological sensing deep in tissue
Optical setup to allow fibre based sensing. A 520 nm laser source (10 µW power and 100 ms exposure) was used as a pump source to excite both the pH and oxygen sensors. The pump illumination was launched from a single mode fibre (SMF) collimated by an aspheric lens (L1), passing through a band pass filter (BP) removing unwanted long wavelength light, and reflected by the dichroic mirror (DM), then focused with an identical aspheric lens (L2) and selectively coupled into the fibre core (with XY control of the sensing fibre mount). The returned light from the fibre core was collimated by L2, passed through the dichroic mirror and a long pass filter (LP, removing any reflected pump light). The fluorescence was then focused by lens L3 into a 50 µm core multimode fibre (MMF) patch cable, and directed to a spectrometer (Ocean Optics QEPro). The triggering unit (TTL pulse generator) controlled both laser and spectrometer allowing on demand short integration time (100 ms) synchronised measurements.
