FSK Signals Research Articles

Polarisation-insensitive, 500 Mbit/s FSK transmission over 153 km by passive polarisation switching

Polarisation-insensitive heterodyne transmission of a 500Mbit/s FSK signal over 153 km of fibre is realised by passive, data-induced polarisation switching. For the first time, this technique is used with a delay-line demodulator.

Performance of binary FSK communications over frequency-selective Rayleigh fading channels

The performance of binary frequency-shift-keyed communications over frequency-selective wide-sense-stationary uncorrelated-scattering Rayleigh fading channels is discussed. Previous analyses of FSK communications over frequency-selective channels have considered the average probability of error for specific models for the fading channel and typically assume that the two FSK signals are orthogonal. A technique for obtaining bounds on the average error probability for FSK in terms of one or two parameters obtainable from multipath spread or frequency correlation functions channel measurements is described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Novel polarisation-frequency conversion-type polarisation diversity optical receiver

A novel polarisation-frequency conversion-type polarisation diversity optical receiver with one photodiode and one demodulator is proposed. A power penalty variation due to polarisation changes within 1 dB is achieved for optical FSK signals. >

FDMA-FSK noncoherent network operated at 600 Mbit/s using two-electrode DFB lasers and fibre optical filter demultiplexer

We demonstrate a two-channel FDMA-FSK star network using frequency-tunable two-electrode DFB lasers. Channels arc demultiplexed by a tunable fibre Fabry-Perot filter, which also converts the FSK signal to ASK format for noncoherent detection. Bit error rates of 10-13 have been measured at 600 Mbit/s transmission rate for (223-1) word lengths. High bit rate and frequency tunability have thus been combined for use in an FDMA.

FSK‐ASK transfer characteristic of the double‐mode oscillator with third harmonic oscillation

AbstractNumerous detailed studies have been made on the injection locking of the solid‐state microwave oscillator, but there have been few applications of the locked multimode oscillator to the communication system. The double‐mode oscillator with the third harmonic oscillation has the feature that it can easily be locked to the external signal and has two kinds of stable locked steady‐states. When an FSK signal is used as the external signal, the signal is converted into ASK signal, and the oscillator operates as an the FSK‐ASK converter. This paper discusses the fundamental operation of the FSK‐ASK converter with the following contents: (1) For the case where the frequency of the injected signal changes stepwise, the transient locking response of the oscillator is analyzed. It is shown that the upper bound for the FSK modulating frequency (modulation rate), for which the FSK‐ASK conversion can be realized, is determined by the rise‐time and the fall‐time and the fall‐time of the oscillator output; (2) the code‐error rate of the ON‐OFF amplitudes of ASK wave is calculated. It is shown that the signal can be detected with an error rate equal to or less than that of the FSK coherent detection; (3) The power spectrum desnsity and correlation time of ASK wave, as well as the noise suppression by the double‐mode oscillator are derived. Finally, an experimental example is shown for the typical basic characteristics, indicating the validity of the theory.

Optical demodulation and amplification of FSK signals using AlGaAs lasers

Stimulated Brillouin scattering is used as a narrowband amplifier to demodulate and amplify FSK signals at bit rates up to 250 Mbit/s. Gain of as much as a factor of 1000 is obtained for a pump power of 12mW. Both pump and signal lasers are simple AlGaAs lasers.

Performance of a frequency-locked 1.3μm DFB laser under 50Mbit/s FSK modulation

A GaInAsP DFB laser modulated with a 50 Mbit/s pseudorandom AMI FSK signal was locked to the 2p10−3d5 transition of argon at 1.2960μm using the optogalvanic effect. No significant degradation in frequency stability due to the modulation was observed. When the signal was demodulated, the power penalty due to the frequency-locking servo loop was found to be less than ⅓dB.

New FSK phase-diversity receiver in a 150 Mbit/s coherent optical transmission system

We present a coherent FSK phase-diversity system with a novel delay-and-cross-multiply frequency discriminator that allows reception of the FSK signals in the baseband. The measured sensitivity is −52 dBm at 150Mbit/s after 52 km of fibre.

Polarisation-insensitive coherent lightwave system using wide-deviation FSK and data-induced polarisation switching

The authors present a technique wherein polarisation-insensitive heterodyne detection is achieved through data-induced polarisation switching. The polarisation switching is brought about by inserting a passive, birefringent optical device in the path of the transmitted FSK signal. The experimental results show that this technique suffers a power penalty of 3-4 dB when compared with a conventional FSK system with perfectly matched polarisations. This compares well with the expected penalty of 3 dB. This approach uses a single optical receiver and no additional receiver electronics, which could be a significant advantage for local area networks. >

Optical 4-ary FSK modulation and demodulation experiment

Experimental results of the new 4-ary FSK modulation and demodulation systems are reported. Two binary signals are directly injected into different electrodes of a 3-electrode DFB-LD, producing an optical 4-ary FSK signal with 1 GHz frequency spacing. For demodulation, two differential detectors convert the 4-ary FSK signal into two binary signals.

Waveform distortion evaluation for optical CPFSK heterodyne transmission

Waveform distortion of a continuous phase FSK signal due to fiber chromatic dispersion is measured. The transmission spacing is estimated to be 100 km at 5 Gbit/s with 1.55-μm wavelength. Also the 2-Gbit/s optical CPFSK heterodyne detection transmission experiment is reported. Since there is no chirping degradation, it is possible to transmit the signal through a 200-km single-mode fiber.

2 Gbit/s optical CPFSK heterodyne transmission through 200 km single-mode fibre

The amplitude distortion of a continuous phase FSK signal due to fibre chromatic dispersion is measured. We also report a 2 Gbit/s optical CPFSK heterodyne detection transmission experiment. Since there was no chirping degradation, it was possible to transmit the signal through a 200 km single-mode fibre.

Discrimination Against Partially Overlapping Interference--Its Effect on Throughput in Frequency-Hopped Multiple Access Channels

In this paper we derive the probability of correct packet reception and the resulting channel throughput achievable in an asynchronous slow-frequency-hopped multiple user channel. Reed-Solomon coding is used to correct errors caused by other-user interference in an otherwise noiseless channel. We analyze and evaluate an M -ary FSK signaling scheme, which permits the discrimination against interfering signals that are present for a sufficiently small fraction of the hop duration, and results in substantial increases in channel throughput over previous models.

Unknown Bounds on Performance in Nakagami Channels

Optimum performance of communication in Nakagami channels is reexamined. With novel functionals of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">m/\gamma</tex> -distribution, analyses of signal interference and of coherent binary detection are greatly simplified. The general error-rate formula holds for coherent and noncoherent detection of PSK or FSK signals. A lower bound on error rates is established for some diversity systems.

Injection locking of a double‐mode oscillator with fundamental and third harmonic resonators

AbstractThe injection locking of the solid‐state oscillator has been studied from the viewpoint of various applications such as modulation, detection, regeneration and amplification of signal in communication systems. The injection locking oscillation with harmonics exhibits various peculiar phenomena which are not observed in the single‐mode oscillator with single resonant circuit. This paper discusses the double‐mode oscillator composed of fundamental and third harmonic oscillations. The major results are as follows: (1) The effective increase of the Q value for the fundamental frequency due to the presence of the third harmonic is evaluated in terms of the effective external Q; (2) It is shown that the locking equation for the phase in the simultaneous oscillation of fundamental and third harmonic frequencies, is of the same expression as that of the basic equation second‐order loop (with imperfect integrator) in the phase‐locked loop (PLL). The equivalent loop gain is defined from such a viewpoint; (3) There exists a jumping phenomenon in the oscillator output, when the frequency of the injection signal is varied. This is the result of a sudden change of the injected signal frequency affecting the amplitude to an on‐off behavior. This property can be applied to the detection of FSK signal. These results of analysis were compared with the experiment, and satisfactory agreement was obtained.

Discriminator with partial response detection of nrz. fsk signals

AbstractIn the TDMA subscriber loop radio communication system, large carrier frequency deviation exists in burst signals from subscribers to a base station. A modulation/demodulation technique, which is suitable for the burst transmission with large frequency variation, is studied in this paper. First, problems in the terrestrial TDMA system and clarified and it is shown that the use of conventional FSK‐discriminator detection causes large CNR degradation due to the variation. Next, differential FSK‐Partial Response Detection (DFSK), which can cope with the frequency variation and has a simple structure, is proposed and its principle and structure are described. Furthermore, the intersymbol interference and adjacent channel interference characteristics are evaluated theoretically and the bit error rate (BER) characteristics are evaluated experimentally. As a result, the optimum modulation index and IF‐band reception band path filter are obtained. Finally, the optimum transmission system of DFSK designed for wide‐band Digital Radio Subscriber Loop System using 26‐GHz band is described. DFSK is shown to be a practical and promising modulation/demodulation system for a terrestrial TDMA communication system, on which a large demand is expected in the future.

S/N and error rate evaluation for an optical FSK-heterodyne detection system using semiconductor lasers

Receiving performance is evaluated for an optical FSK-heterodyne detection system in which semiconductor lasers are used as both an FSK transmitter and an independent local oscillator. Noise and error rate are measured under feedback stabilization of IF signal frequency and electrical equalization of semiconductor laser FM modulation frequency characteristics. The minimum received signal power of -44 dBm, which is about 2 dB better than that in IM direct detection, is achieved at a 10-9error rate for a 200 Mbit/s signal. Excess errors for FSK signals result from frequency broadening of the laser spectrum. Both AM and FM quantum noises in the lasers are primary factors which determine system performance. Error rate characteristics in an optical FSK direct detection system, in which a Michelson interferometer is employed as an optical frequency discriminator, are compared with the above results.

Detection of FSK and DPSK data signals by pulse compression

Detection of FSK and DPSK data signals by pulse compression

Optical FSK signal detection in a heterodyne system using semiconductor lasers

A 10−8 bit error rate is achieved for 100 Mbit/s signals in an FSK heterodyne frequency-discrimination detection system, in which AlGaAs double-heterostructure lasers are used as both the FSK transmitter and the local oscillator. Receiving signal power level to achieve a low bit error rate is experimentally obtained, which confirms the principle of optical heterodyne detection. AM quantum noise in the laser local oscillator and FM quantum noise are important factors which determine the system performance.

Semiconductor laser FSK modulation and optical direct discrimination detection

FSK signals are generated in an AlGaAs double heterostructure laser by employing an electrical equalising circuit to compensate for its nonuniform FM modulation characteristics. A 10?9 bit error rate is achieved at a 100 Mbit/s data rate in the optical direct discrimination detection with a Michelson interferometer. The optical FSK discrimination detection performance is studied in terms of receiving signal power level and laser spectral linewidth.