We demonstrate a laser Doppler velocimeter (LDV) based on self-mixing effect in a single longitudinal mode VCSEL
for velocity measurement of flowing milk using Polymer Optical Fiber (POF). We find that self-mixing signal in
frequency domain was broadened using POF compare with space coupled. The flow velocity was measured when POF
outside and inside the milk. Their self-mixing signals of power spectrum can be fitted with Gaussian and exponential
decay function, respectively. The differences of self-mixing signal in frequency domain when POF outside and inside
milk are discussed. Due to POF have the advantages of flexibility and compatible with biology, this velocimeter can also
be used for the measurement of blood flow in vivo.
Inexpensive PMMA based Polymer Optical Fiber (POF) has the feature of a large core diameter, high numerical aperture and great flexibility, thus allow low connection cost and cheap LED source. These advantages make it a promising candidate for short distance communication. In this article, coarse wavelength division multiplexing (CWDM) test was performed with commercially available POF using its low loss transmission window. Light of two different wavelengths (650nm and 530nm) were sending on a single POF. Here 650nm red light was used for duplex IP data digital signal transmission and 530nm green light was used for voice signal transmission. Light sources are LEDs. A POF Coupler (Splitter) of 1:1 ratio was employed as multiplexer and prisms were used for demultiplexing. The channel isolation and insert loss of both channels were measured, for 650nm channel they are 20.5dB and 17.65dB, for 530nm channel they are 19.16dB and 20.55dB.