Patent ID: 6320179
Filing Date: 2001-11-20
Classification: H01S

Abstract:
A system for measuring one or more noise contributions to an optical output signal, OPT.sub.DUT, (3) from a device (1) comprising;means (19) for generating a broadband, substantially shot noise limited optical reference signal, OPT.sub.REF, (21),detection means (10) for receiving the optical signals, OPT.sub.DUT and OPT.sub.REF, (3, 21) and converting said optical signals into equivalent electrical signals, ELEC.sub.DUT and ELEC.sub.REF respectively, each comprising an ac component and a dc component (13), wherein the dc components (13) of the electrical signals, ELEC.sub.DUT and ELEC.sub.REF, are substantially equal,means (12) for separating the ac components and the dc components (13) of the electrical signals, ELEC.sub.DUT and ELEC.sub.REF,means (14) for measuring the dc components of the electrical signals, ELEC.sub.DUT and ELEC.sub.REF,means (16) for amplifying the ac components of the electrical signals andmeans (18) for measuring the amplified ac components of the electrical signals at a plurality of frequencies, whereby the measurement of at least one of the ac components or dc components (13) of the electrical signals, ELEC.sub.DUT and ELEC.sub.REF, provides an indication of one or more of the noise contributions to the optical output signal, OPT.sub.DUT (3).