Bidirectional optical communications having quick data recovery without first establishing timing and phase lock

Abstract

A method of transmitting and rapidly recovering a burst of data without first having to establish a timing or phase lock. The signals are transmitted as modified Manchester coded signals having pulse transitions at a clocking pulse rate which is a multiple of the clocking pulse rate at which the signals are originally generated, and wherein the MOOSE coded signal is modified by ON-OFF keying.

Description

RELATED APPLICATIONS [0001] This application is a continuation application of U.S. application Ser. No. 09 / 723,804 filed Nov. 28, 2000.TECHNICAL FIELD OF THE INVENTION [0002] The present invention relates generally to methods and apparatus for providing FTTH (Fiber to the Home) bidirectional communications over a single optical fiber, and more specifically to NRZ (Non-Return to Zero) coded signals at a first frequency transmitted downstream and a Manchester coded signal at a second frequency modified by ON-OFF keying and transmitted upstream. The upstream and downstream coded signals are both used to modulate a carrier light wave having a selected wavelength of light, such as, for example, 1310 nanometers of light. The invention further relates to methods and apparatus for transmitting and recovering bursts of data with a minimal number of preamble bits and without first requiring phase lock. BACKGROUND OF THE INVENTION [0003] The communications industry is using more and more optic...

AI Technical Summary

Benefits of technology

[0010] Shortcomings of the above-discussed bidirectional communication system are overcome by the apparatus and methods of the present invention which comprises generating a first NRZ (Non-Return to Zero) data stream having a first clocking frequency and then transmitting the first NRZ data stream by an optical fiber from a first location to a second location. The data stream is transmitted by modulating a carrier having a selected wavelength of light such as, for example, 1310 nanometers. The selected wavelength of light from the first location is received at the second location and the NRZ data stream is recovered. A second NRZ data stream intended for travel to the first location and also having the first clocking frequency is converted to a Manchester coded data stream at the first clocking frequency. The Manchester coded data stream frequency is then further modified by ON-OFF keying at a second frequency which is a selected multiple of the first clocking frequency, such as, for example, eight times (8×) the first clocking frequency. A particular combination coding discloses as a preferred embodiment herein as MOOSE (Manchester OOK Serial Encoding). The modified combination coded data stream or MOOSE coded data stream generated at the second location is transmitted to the first location by the same optical fiber used by the first NRZ coded data stream and at the same selected wavelength of light. The modified MOOSE coded data stream is then received at the first location where it is converted back to an NRZ data stream having the first clocking frequency without having to first determine clocking signals or establish phase lock loop by reconstructing the Manchester code. The reconstruction is accomplished by delaying the combination coded data stream for a period of time substantially equal to one-half cycle of the second frequency and then combining the delayed signal with an undelayed stream of the combination coded signal.

Problems solved by technology

However, as mentioned above, optical fibers have extremely high bandwidths and use of an optical fiber as a single bidirectional telephone channel is a very ineffective use of the fiber and, in fact, the available bandwidth of an optical fiber is what makes it possible to use two different and unrelated transmission techniques such as the transmission of bidirectional TDM telephone techniques at one wavelength, and the use of another technique, such as straightforward broadcasting of TV signals downstream at a second wavelength.

A major problem for the bidirectional telephony signals is light reflection typically occurring at optical connections or interfaces along the optical fiber, and in a worse case situation, the reflected energy may be interpreted as an actual signal transmission in the bidirectional communication.

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