Subtracting analog noise from an optical communication channel using stable, non-absorbing optical hard limiters

US6516106B2 · kind B2 · utility

Assignee

• Nortel Networks Limited · CA

Inventors

• Erik Johnson · Toronto, CA
• Edward Hartley Sargent · Toronto, CA

Key dates

• Filing date: Aug 20, 2001
• Grant date: Feb 4, 2003
• Expiry date: Aug 20, 2021

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04B10/2507
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

Analog noise is subtracted from an optical communication channel using stable, non-absorbing optical hard limiters. A reference signal B is combined with a control signal of intensity I2 through a 3 dB optical coupler to form a first combined signal having an intensity substantially equal to (B/2+I1). The first combined signal is processed by a first optical hard limiter to form a reflected signal having an intensity substantially equal to (I1−B/2). An information signal A is combined with a bias signal of intensity I2 through a 3 dB optical coupler to form a second combined signal. The reflected signal and the second combined signal are combined through a 3 dB optical coupler to form a third combined signal having an intensity substantially equal to 0.5(I1−B/2+A/2+I1). The third combined signal is processed by a second optical hard limiter to form a transmitted signal having an intensity substantially equal to 0.5(A−B). I2 is substantially equal to two times I1.