Showing papers on "Optical Carrier transmission rates published in 1988"

Efficient narrow‐band direct modulation of semiconductor injection lasers at millimeter wave frequencies of 100 GHz and beyond

Abstract: It has been demonstrated both theoretically and experimentally that it is possible to mode lock semiconductor lasers at millimeter wave frequencies approaching and beyond 100 GHz. The mode‐locked output usually takes the form of sinusoidal modulation, and can be regarded for practical purposes as a highly efficient means of directly modulating an optical carrier in a narrow band at millimeter wave frequencies. In active mode locking, the external signal efficiently creates the optical modulation, while in passive mode locking a small external signal imposes its information on the optical carrier by injection locking the passive mode‐locked output. Experimentally, we have demonstrated passive mode locking at 70 GHz using a tandem contact GaAs laser.

Wavelength-tunable 16 optical channel transmission experiment at 2 Gbit/s and 600 Mbit/s for broadband subscriber distribution

Abstract: We report a 16 optical-channel single-mode fibre transmission experiment based on dense-WDM and tunable-etalon channel selection. Experiments at 2 Gbit/s and 600 Mbit/s over 10 km of single-mode fibre show little crosstalk penalty when the optical channel spacing is 2 nm. The system architecture is useful for high-capacity broadband subscriber distribution.

Demodulation technique for coherence multiplexed optical data transmission system

Abstract: An improved demodulator and demodulation method usable in a coherence multiplexed, optical data transmission system. The demodulator comprises an interferometer and a signal processor. The interferometer has first and second arms having first ends coupled to receive radiation from an optical bus, and second ends connected to the signal processor. The path length difference between the arms is selected to approximately match that of a corresponding modulator, to within the coherence length of the optical carrier. The signal processor processes the optical signals emerging from the arms in combination, to produce a pair of electrical ouput signals. Linearly independent pairs of electrical ouput signals are produced for any two modulation signals that do not produce modulator optical path length differences that differ from one another by an integral multiple of a half wavelength of the optical carrier. In a preferred embodiment, the electrical output signals correspond to the cosine and sine of the phase modulation angle produced in the associated modulator.

Simultaneous transmission of 100 Mbit/s at baseband and 60 FM video channels for a wideband optical communication network

Abstract: A wideband optical communication system is demonstrated over 12 km of optical fibre which simultaneously transmits both a 100 Mbit/s baseband digital signal and 60 FM video channels subcarrier multiplexed in the 2.7–5.2 GHz band.

A low crosstalk microoptic liquid crystal switch

Abstract: A total internal reflection liquid crystal optical switch has been developed which gives crosstalk levels of -33 dB and switching speeds of 4 ms, with low operating voltage. A novel architecture for larger switch arrays is also proposed and prototype device constructed and tested. The effects of modulation on the optical carrier by the electrical drive signal, and methods of minimizing its effect are reported. Finally, a novel space-saving architecture is proposed and demonstrated for 4*4 switch arrays and its performance reported. >

Simultaneous single-fibre transmission of video and bidirectional voice/data using LiNbO/sub 3/ guided-wave devices

Abstract: A system experiment which uses integrated optics to effect bidirectional transmission on a single-mode fiber is described. The system has practical applications and provides more functionality than previously reported experimental systems. The system consists of a video link (180 Mbit/s) and a voice/data link (1.54 Mbit/s) to the end user and a return voice/data link (1.54 Mbit/s) from the end user. Two LiNbO/sub 3/ devices are used to externally modulate lasers and a third is used in a novel way to demultiplex the incoming signals and to eliminate the need for an optical source at the user's end. The system operated over 4 km of standard single-mode fiber with a BER >

Sharing of the optical band in local systems

Abstract: Ways of supporting large numbers (on the order of thousands) of simultaneous high-speed ( approximately 10 Mb/s) users on the lowest hierarchical unit of a coherent optical system are investigated. Assuming each channel uses a different optical carrier, a key impairment is laser phase noise, which causes modulated optical carriers, nominally widely separated in frequency, to not be truly spectrally disjoint. To deal with this problem in consideration of the superabundance of optical bandwidth, attention is focused on the region of low spectral utilization. For this region, formulas are derived that describe the performance of three arrangements of optical channels: equally spaced carriers, randomly placed carriers, and randomly placed carriers with spread spectrum. The formulas quantify the great superiority of equally spaced carriers over random placement, despite the highly significant benefit afforded by spread spectrum. Numerical examples are worked out to show this result. >

Calibration of optical receivers and modulators using an optical heterodyne technique

Abstract: A dual Nd:YAG ring laser heterodyne system for the calibration of optical receivers is presented. This heterodyne system offers more than 50 dB of dynamic range. Calibration of optical phase and amplitude modulators is achieved by downconverting a sideband of the modulated optical carrier to a fixed intermediate frequency with another laser. This technique eliminates the need for a high-speed receiver. This dual YAG system is capable of generating beat frequencies from DC to more than 100 GHz. >

A coherent optical system for analogue multichannel video transmission

Abstract: A heterodyne analogue system using optical phase modulation is well suited for analogue transmission of CATV signals with a large number of videochannels. The authors describe the realisation of a heterodyne transmission system using optical phase modulation and nonsynchronous demodulation. In the experimental setup 18 standard FDM multiplexed TV channels (PAL system) are modulated onto a single optical carrier; the system concept allows transmission of 30 channels. The power budget allows a further increase in capacity by using multiple (at least 10) optical carriers in optical FDM, each carrying 30 TV channels. In order to meet the stringent phase noise requirements, two novel concepts are presented for phase noise reduction: optical filtering and phase-noise compensation based on linear heterodyne detection. For reduction of the required receiver bandwidth, a new detection scheme has been developed, offering simultaneous phase diversity, intensity noise suppression and frequency demodulation with only two photodiodes.

Optical Generation And Distribution Of Microwave Signals

Abstract: We report the results of the optical generation of microwave signals superimposed as a modulation on an optical carrier by means of laser heterodyning. The modulated optical carrier can be easily distributed with fiber-optic cables. This approach offers microwave distribution advantages in size, weight, cost, and frequency diversity, which are desirable in improtant applications such as phased antenna control.

Analytical model for semiconductor laser amplifiers in coherent optical systems

Abstract: A model based on a full travelling-wave analysis of a semiconductor laser amplifier is applied to calculate the increase in spectral linewidth of an unmodulated optical carrier passing through the amplifier. This linewidth can then be used in system performance calculations for a coherent optical transmission system employing laser amplifiers along the fibre link.

Single laser optical communication system and method

Abstract: The invention describes a method for optical communication of information between transmitter and receiver spatially separated from each other. The principle of heterodyne reception is utilized. A non-modulated optical carrier of a laser arranged on the receiving side is subdivided in a first fiber-optical coupler KE into two portions, the transmission path EMF and the local laser wave LL. In one branch, a displacement of frequency by the amount of Δf takes place. The non-modulated optical carrier passes through a one-mode fiber EMF in direction transmitting side and is modulated there with an effective signal in a modulator MOD (FIG. 1). This now modulated optical signal travels back to the receiving side, where it is converted with the local laser wave LL into an intermediate frequency band.

A 1/N countdown timing extraction circuit for a gigabit optical fiber transmission system

Abstract: A new timing extraction method for a gigabit optical fiber transmission system has been proposed. Its performance has been verified through a 2.4Gbps optical fiber transmission experiment. The extracted timing signal exhibits 1.2deg. RMS jitter, and gives-27.9dBm receiver sensitivity at 10/sup -9/ bit-error-rate.

Demonstration of optical drop-and-insert for accessing 2.24 Gbit/s optical transmission systems directly at the 140 Mbit/s level

Abstract: Optical drop-and-insert of 140 Mbit/s channels is demonstrated on a 2.24 Gbit/s bit-interleaved transmission system. Individual channels can be accessed optically, and synchronisation of the local station is carried out without the need for high speed clock extraction.

Fibre optic sensor multiplexing by FMAMCW

Abstract: An intrinsic quasi-distributed optical fibre sensor network composed of three intensity-modulated fibre sensors has been assembled to study the sensor response signal multiplexing performances. A frequency-modulated RF continuous wave Ft is used to modulate the intensity of the optical carrier emitted by a laser diode. The performances and operating conditions of two detection schemes, one digital and one analogue, have been presented and discussed. The first method makes use of three narrow parallel digital filters centred on each sensor signal frequency. The authors have obtained a signal-to-noise ratio of 40 dB and a cross-talk level lower than the noise for a signal frequency separation ratio of 1.2. The sensor modulation bandwidth is limited by the data acquisition time and the computing time to about 10 Hz. The analogue detection consists of an analogue filter and a linear phase-locked loop. The synchrone detection delivers a signal-to-noise ratio of 40 dB with an integration time constant of 100 ms. With sensor signals of equal intensity the cross-talk is lower than -40 dB. The sensor modulation bandwidth is limited by the sensor signal frequency separation to about a tenth of that value.

Measurements On A 2 Km Broadband Atmospheric Optical Communications Link For Video And Data

Abstract: This paper reports on observed preliminary transmission performance of frequency-division multiplexed NTSC video and DS1 channels modulated on to an optical carrier and transmitted over a two-kilometer atmospheric path in New Jersey, USA, with emphasis on measurements made during the fall of 1987. At a distance of two-km, the received laser beam footprint was set at 8 feet in diameter to accommodate temperature related beam wander. The received signal was processed to retrieve the video and data signals. Transmission path fading was monitored using a tone signal over an adjacent parallel path. DS1 bit-error ratio and video signal parameters were monitored according to established standards. Link deployment issues, optical power budgets and preliminary performance results are reported. The Conditions under which system failures were observed are described.