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Green LEDs boost POF transmission

06 Feb 2003

Researchers say their 509 nm LED will maximise transmission distances in plastic optical fiber.

Plastic optical fiber (POF) has long been touted as an ideal medium for short-distance data transfer, offering the potential for low-cost, robust connectivity within homes, apartment blocks or offices. Most commercial POF systems operate with a transmission wavelength of 650 nm, but a lower fibre loss can be found at around 510 nm.

To exploit this attenuation minimum, the photonics group at the NMRC in Ireland developed an LED that emits at 509 nm and used it to transmit 200 Mbit/s of data through 100 m of POF. The NMRC, working in collaboration with the Centre de Recherche sur l'Hétéroépitaxie et ses Applications in France and Infineon Technologies in Germany, fabricated InGaN/GaN LEDs with a total output power of 1.2 mW at 20 mA.

The sources exhibited a wavelength shift of just 0.042 nm/K and a power variance of --0.28 %/K at 20°C. The researchers performed bandwidth measurements on standard polymethyl methacrylate-based step-index POF with a 1 mm core and a numerical aperture of 0.3. At a transmission wavelength of 509 nm, the fiber's attenuation loss was 0.13 dB/m, down from 0.18 dB/m at 650 nm.

Author
Tami Freeman is technology editor of Fibre Systems Europe magazine.

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