A cable television system (100) having forward and reverse paths includes, in the reverse path, a digital optical transmitter (200) for receiving an RF signal, converting it to a digital signal, and adding a digital pilot tone thereto. A laser is driven in accordance with the summed digital signal to generate a digital optical signal representative of the pilot tone and the RF signal. The cable television system (100) also includes an optical receiver (305) for receiving the digital optical signal and recovering therefrom the RF signal and the pilot tone. The optical transmitter (200) and receiver (305) are coupled by fiber optic communication media (110).

Digital optical transmitter

A multimode optical fibre communications system, and in particular to a system in which non-linearities in the propagation of the signal through a multimode optical communications channel degrade the signal presented to the receiver. The system includes an optical transmitter unit for connection to a multimode optical fibre transmission link. The transmitter unit has a data input for receiving an input data signal, a data signal processing circuit and a source of optical radiation. The data signal processing circuit is arranged to receive the input data signal from the data input and to provide a processed data signal to the source of optical radiation and the source of optical radiation is arranged to generate from this an optical signal for transmission by a multimode optical fibre. The data processing circuit is arranged to provide from the input data signal a non-inverted data signal and an inverted data signal, receive a control signal for controlling the generation of the processed data signal, apply a controllable delay in accordance with the control signal to at least one of the non-inverted and inverted data signals, and combine the non-inverted and inverted signals after the application of the controllable delay(s) and gain factor(s) to generate the processed data signal.

Multimode optical fibre communication system

Method and apparatus for an analog FM optical link having a low noise figure and a high spurious-free dynamic range. In one embodiment, the apparatus includes a FM DFB laser and a balanced receiver. The balanced receiver includes an optical splitter to split the received beam into two optical paths. Each of the two paths includes an optical filter and a photodetector. A differentiator coupled to the electrical output of the photodetectors produces a demodulated electrical signal in response to the RF signal used to modulate the DFB laser. This configuration can eliminate the laser relative intensity noise and second order harmonics. In addition, third order distortion is eliminated when there is no intensity modulation or greatly reduced when intensity modulation is present.

All-optical analog fm optical receiver

A method and system for enhancing digital video transmission to set-top boxes improves the performance of a hybrid analog and digital video transmission system, for example, an AM-VSB QAM video transmission system, by selecting a digital channel map based on the relative magnitude and frequency locations of CSO and CTB distortions and the analog channel frequency plan. A variable interleaver may also be implemented in the video transmission system to further reduce the CSO and CTB distortions.

Method and system for enhancing digital video transmission to a set-top box

A transceiver architecture for wireless base stations wherein a broadband radio frequency signal is carried between at least one tower-mounted unit and a ground-based unit via optical fibers, or other non-distortive media, in either digital or analog format. Each tower-mounted unit (for both reception and transmission) has an antenna, analog amplifier and an electro-optical converter. The ground unit has ultrafast data converters and digital frequency translators, as well as signal linearizers, to compensate for nonlinear distortion in the amplifiers and optical links in both directions. In one embodiment of the invention, at least one of the digital data converters, frequency translators, and linearizers includes superconducting elements mounted on a cryocooler.

Digital radio frequency transceiver system and method

The AM/FM converter of the present invention comprises an optical frequency modulation section which receives multi-channel AM video signals and outputs an optical-frequency-modulated optical signal beam; and an optical heterodyne detection section comprising an optical frequency oscillator composed of a semiconductor local laser which outputs a local oscillator optical beam having an optical frequency separated by a designated intermediate frequency, an optical coupler, and a photoelectric converter composed of a photodiode, which receives the optical signal beam and outputs an electrical batched FM modulation signal which is frequency-modulated and frequency-converted to the intermediate frequency By means of this configuration, the invention offers an AM/FM converter wherein the frequency band is made considerably wider

AM/FM converter and optical signal transmission system

Dans le reseau optique presente, on utilise la technique de multiplexage optique par repartition en frequence pour la transmission en aval et la technique d'acces multiple par repartition dans le temps pour la transmission en amont. Des exemples, des problemes et des avantages du reseau sont presentes

New optical star-bus network for subscriber

An apparatus, system and method for transmitting an FM batch converted signal and another signal via the same optical fiber transmission path. For example, a first signal such as a CATV signal or the like (90-770 MHz) is FM batch converted, then this FM batch converted signal (0-6 GHz) is frequency multiplexed with a second signal such as a BS/CS satellite RF signal or the like (11.7-12.8 GHz), and then these multiplexed signals are transmitted as an optical signal via an optical fiber. The optical signal received via the optical fiber is photo-electrically converted by a single light receiving element such as a PD or the like, then applied through a preamplifier and then frequency separated by a filter or the like. The frequency separated FM batch converted signal is FM demodulated to recover the first signal, while the frequency separated second signal is converted to an IF signal (1030-2070 MHz) by a BS/CS converter. The center frequency of the FM batch converted signal is appropriately established, thereby minimizing the affection of spurious interference.

Optical signal transmission apparatus, system and method

According to the present invention, an apparatus, a system and a method for transmitting a FM batch converted signal and another signal on the same optical fiber can be provided. For example, a first signal such as CATV signal may be FM converted in batch. This converted signal may then be frequency-multiplexed with a second signal such as BS/CS satellite broadcasting RF signal to transmit over optical fiber as an optical signal. The optical signal transmitted via the optical fiber is photoelectrically converted by a single photo-receiving element and is frequency-separated by a filter after passing through a preamplifier. The frequency-separated, FM batch converted signal is FM-demodulated and restored to the first signal, and the frequency-separated second signal is converted to an IF signal by a BS/CS converter. With appropriate setting of the center frequency of the FM batch converted signal, the influence by spurious interference can be minimized.

Apparatus, System And Method For Optical Signal Transmission

A wavelength multiplex transmission system is provided to reduce crosstalk among wavelengths and reduce deterioration of signals. At a transmission apparatus, one input signal is differentially divided into two; each of the two is converted to an optical signal; and then they are wavelength-multiplexed and transmitted. When crosstalk is arisen in the wavelength multiplex transmission system, the crosstalk is superposed on the two optical signals. The crosstalk is equally superposed on each of the signals with inverted polarities. Accordingly, converting the optical signals to electrical signals and then differentially combining them at a receiving apparatus, their signal components are accumulated, while their crosstalk components are cancelled out. Thereby, in the wavelength multiplex transmission system, deterioration of optical signals due to crosstalk can be reduced.

Koji Kikushima

Papers

AM/FM converter and optical signal transmission system

New optical star-bus network for subscriber

Optical signal transmission apparatus, system and method

Apparatus, System And Method For Optical Signal Transmission

Wavelength multiplex transmission system