Tuesday, June 1, 2010

More on using visible light for data communication

Tech-on carries another news item about using visible light for data transmission:
The visible light communication system was developed by Outstanding Technology Co., Ltd. of Japan, a technology start-up. Performance in the lab has achieved transmission of a digital signal at 160Mbit/s over a 20cm distance with a single LED, and 13km transmission of a 1kbit/s-equivalent analog voice signal.
The firm combined a silver mirror with the photoreceptor to boost sensitivity and speed simultaneously. Concretely, light not directly received by the photoreceptor is reflected from the surrounding parabolic silver mirror into it.
The larger effective receptor area made it possible to use a high-speed (400MHz cut-off) photoreceptor and still achieve a high sensitivity of 1.5A/W to 2A/W output through 450nm wavelength. This is roughly ten times more sensitive than other photoreceptors with comparable waveband and speed.
While details of the new technology are still unknown, it was revealed that the modulation circuit design was based on accurate measurement of white LED resistive, capacitive and inductive components, making the success possible.

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