Event Details

Advances in Optical Fiber Amplifiers

Presenter: Dr. William Wong - Sr. Optical Engineer, Altamar Networks, Mountain View, California
Supervisor:

Date: Wed, April 30, 2003
Time: 14:30:00 - 15:30:00
Place: EOW 430

ABSTRACT

Abstract

Fiber optics is now the preferred technology for the transmission of information over long distances. This technology, based on semiconductor lasers and optical fibers, is used to transmit voice, data, and video information. To overcome material loss in optical fibers, we place optical fiber amplifiers periodically along a transmission line to re-amplify the signal. It is important that we study and explore the operation of these amplifiers so as to optimize the quality of signal transmission. In addition, gain transients in erbium-doped fiber amplifiers and in Raman amplifiers are created in a dynamic optical network where wavelength channels are added/dropped at every access node. We need to study and suppress these amplifier gain transients as their presence degrades the quality of transmission.

In this seminar, discussion will focus on our recent observation and modeling of gain dynamics in Raman amplifiers, along with a control scheme for suppressing these gain transients. The usefulness of a new technique for making time-resolved measurements of bit error rate (BER) and optical signal-to-noise ratio (OSNR) will be demonstrated. As an example, we measured the BER and the OSNR of a surviving channel as the channel loading was varied by 100%. A severe drop of 5 dB in OSNR was observed despite the fact that the channel power decreased by 3 dB only.

Finally, our observation of four-wave mixing (FWM) between co-propagating pumps and signals in a Raman amplifier when the zero dispersion wavelength of the transmission fiber lies symmetrically between the pump and the signal wavelengths will be reported. The resultant FWM products, which grow as they experience Raman gain along the fiber, can degrade the signal's OSNR by as much as 10 dB for a Raman on-off gain of 15 dB.

For Further Information Contact
Dr. N.J. Dimopoulos (721-8902)