Heterodyne based optical spectrum analysis with controlled optical attenuation

An optical heterodyne detection system includes an attenuator for attenuating an input signal before the input signal is combined with a local oscillator signal. An optimal attenuation level for the input signal, which improves the signal to noise ratio of the heterodyne beat signal, is determined b...

Ausführliche Beschreibung

Gespeichert in:

Bibliographische Detailangaben
Hauptverfasser:	MCALEXANDER WILLIAM IAN, BANEY DOUGLAS M
Format:	Patent
Sprache:	eng
Schlagworte:	COLORIMETRY DEVICES OR ARRANGEMENTS, THE OPTICAL OPERATION OF WHICH ISMODIFIED BY CHANGING THE OPTICAL PROPERTIES OF THE MEDIUM OF THEDEVICES OR ARRANGEMENTS FOR THE CONTROL OF THE INTENSITY,COLOUR, PHASE, POLARISATION OR DIRECTION OF LIGHT, e.g.SWITCHING, GATING, MODULATING OR DEMODULATING ELECTRIC COMMUNICATION TECHNIQUE ELECTRICITY FREQUENCY-CHANGING MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT,POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRA-RED,VISIBLE OR ULTRA-VIOLET LIGHT MEASURING MEASURING ANGLES MEASURING AREAS MEASURING IRREGULARITIES OF SURFACES OR CONTOURS MEASURING LENGTH, THICKNESS OR SIMILAR LINEARDIMENSIONS NON-LINEAR OPTICS OPTICAL ANALOGUE/DIGITAL CONVERTERS OPTICAL LOGIC ELEMENTS OPTICS PHYSICS RADIATION PYROMETRY TECHNIQUES OR PROCEDURES FOR THE OPERATION THEREOF TESTING TRANSMISSION
Online-Zugang:	Volltext bestellen
Tags:	Tag hinzufügen Keine Tags, Fügen Sie den ersten Tag hinzu!

Beschreibung
Zusammenfassung:	An optical heterodyne detection system includes an attenuator for attenuating an input signal before the input signal is combined with a local oscillator signal. An optimal attenuation level for the input signal, which improves the signal to noise ratio of the heterodyne beat signal, is determined by obtaining a base measurement of an output signal in response to the local oscillator signal and in the absence of the input signal, obtaining sample measurements of the output signal in response to the input signal as a function of different attenuation levels, and determining the optimal attenuation level as a function of the base measurement and the sample measurements. A minimum attenuation level for the input signal, which protects receiver photodetectors from being saturated or damaged, is determined by setting an initial attenuation level and gradually reducing the attenuation level until the voltage limit of the photodetectors is reached.