Optical transmitter for the common transmission of analog signals and digital qam signals

US5483373A · kind A · utility

Assignee

• Alcatel N.V. · NL

Inventors

• Henning Bulow · Kornwestheim, DE
• Heinz Krimmel · Ditzingen, DE

Key dates

• Filing date: Jun 10, 1994
• Grant date: Jan 9, 1996
• Expiry date: Jun 10, 2014

Classification

• Technology area (CPC H): Electricity
• CPC primary: H04B10/58
• WIPO field: Telecommunications
• WIPO sector: Electrical engineering

Abstract

An optical transmitter for the joint transmission of analog and digital signals is indicated, which, although it contains an optical transmitting component (5) with a laser, does not exhibit an increase in the bit error rate when transmitting the digital signals, due to so-called clipping. The clipping, a negative overmodulation of the laser to below the laser threshold, which occurs because of the constructive interference of the analog signal carders, is prevented by a limiter (8) located upstream of the modulation input of the optical transmitting component (5). The limiter contains a time-variant network that supplies a specified minimum voltage to the modulation input every time a comparator (7) determines that the modulation voltage has dropped below the predetermined threshold.