Accession Number:

AD0603622

Title:

HETERODYNE DETECTION IN OPTICAL COMMUNICATION.

Descriptive Note:

Final rept.,

Corporate Author:

CONTROL DATA CORP MELVILLE N Y TRG DIV

Report Date:

1964-07-01

Pagination or Media Count:

307.0

Abstract:

The properties of optical heterodyne detection are analyzed and measured, using a laser and Twyman-Green interferometer. It is shown that heterodyne amplification preserves the signal-to-noise ratio in the detected difference frequency in the presence of incoherent noise and that the limiting noise of the system is photocurrent shot noise. Suitability of this technique is demonstrated for diffuse as well as specular mirrors and corner reflectors as well as flats. Various techniques of modulation are discussed and demonstrated, including phase, amplitude and single-sideband modulation. A method is developed for the demodulation of phase-modulated light. The limitations imposed on the optical heterodyne technique by the transmission path conditions are investigated. Single-sideband vs double-detection techniques are compared experimentally, under turbulent atmospheric conditions. The former proves to be the superior technique. Design and construction of a field instrument embodying this principle is initiated. The uses and limitations of heterodyne detection in optical communications, demultiplexing of channels, demodulation of FM and AM, Doppler and displacement measurements, and laser stabilization are discussed. Recommendations are made for future research and development. Author

Subject Categories:

Distribution Statement:

APPROVED FOR PUBLIC RELEASE