AT&T Co engineers have just publicised the details of an experimental lightwave telecommunications system that they reckon operates at twice the capacity of highest-capacity systems available at the moment. The test rig used a combination of Wavelength Division Multiplexing and optical amplifiers. The Wavelength Division Multiplexing concept aims to get the most out of optical fibre by transmitting pulses of light of a number of different frequencies over multiple wavelengths. Optic al amplifiers are spliced-in segments of optical fibre containing the rare earth element Erbium; they boost lightwave signals travelling through the fibre. Although the trial took place last year, results weren’t announced until a seminar last month. The team says that it operated the system at 6.8Gbps by transmitting 1.7Gbps over each of four wavelengths of light. The field trial involved transmission of optical signals over 525 miles of dispersive fibre with the optical amplifiers placed 44 miles apart. These trials are part of a feasibility study for next-generation lightwave systems, said Jonathan Nagel, of the Lightwave Hardware Development Department at AT&T Bell Laboratories. The trialists say they used standard single-mode fibre and off-the-shelf transmission equipment, other than the in-line optical amplifiers.
