Showing papers on "Frequency-division multiplexing published in 1984"
TL;DR: State-of-the-art and systems applications of single-mode wavelength-division multiplexing (WDM) devices are described and development trends and problems of the new technology are discussed.
Abstract: State-of-the-art and systems applications of single-mode wavelength-division multiplexing (WDM) devices are described. The performance characteristics required differ depending on whether the method of operation is one-way or two-way. Development trends and problems of the new technology are discussed.
115 citations
TL;DR: A frequency translation technique that effectively enhances the Q of the filter to >100 is presented, which is applicable to the design of a filter with an effective Q of much greater than 100.
Abstract: A circuit for extracting signaling information from its associated voice channel in frequency-division multiplexing has been integrated in metal gate CMOS technology. It uses a frequency translation technique that effectively enhances the Q of the filter to >100. It contains a programmable prefilter, a programmable modulator, and a highly selective bandpass filter. The frequency translation was accomplished through the use of a balanced modulator, which is well suited to a switched-capacitor realization. Design considerations that must be addressed in choosing an optimum architecture and a method of analyzing the ill effects of aliasing in a sampled data modulator were also presented. The technique described here is applicable to the design of a filter with an effective Q of much greater than 100.
62 citations
TL;DR: In this paper, light from two InGaAsP injection lasers of different wavelengths was multiplexed into a 15 km-long single-mode fiber, and due to the nonlinear refractive index, the phase of light in one channel was changed by power changes in the other channel.
Abstract: Light from two InGaAsP injection lasers of different wavelengths was multiplexed into a 15 km-long single-mode fibre. Owing to the nonlinear refractive index, the phase of light in one channel was changed by power changes in the other channel. A 1 mW power charge in one channel produced a 1.4° phase shift in the other channel.
50 citations
TL;DR: In this article, a 9-channel single-mode grating wavelength division multiplexing scheme is demonstrated at 1.5 μm with insertion losses as low as 1.1 dB, with an array of fibres with core-to-core spacing of 36 μm acting as a channel concentrator.
Abstract: A 9-channel single-mode grating wavelength-division multiplexing scheme is demonstrated at 1.5 μm with insertion losses as low as 1.5 dB. An array of fibres with core-to-core spacing of 36 μm acts as a channel concentrator giving a channel separation of 20 A and channel width of 2 A.
30 citations
Patent•
29 Aug 1984TL;DR: In this paper, a key memory containing n keys is provided in each subscriber terminal device with an activation signal decoder ASD connected upstream in order to decode n-1 key addresses.
Abstract: In a telecommunications network, in particular a mobile radio network, with a plurality of subscriber terminal devices and at least one central station, the encryption provided for data prone to misuse, such as subscriber identifiers, is intended to be modified by the central station in a network-uniform manner in the event of the key becoming known. For this purpose, a key memory SP containing n keys is provided in each subscriber terminal device with an activation signal decoder ASD connected upstream in order to decode n-1 key addresses. In the event of misuse of the initially used first key being detected, a network-uniform activation signal AS which is inserted in a concealed manner in the useful signal is transmitted by the central station over a relatively long time period to the subscriber terminal devices, said activation signal providing one of the subsequent n-1 keys instead of the first key. The activation signal AS can be concealed in the useful signal in time division multiplexing, e.g. through permutation of an address bit in an address block which is inserted in the useful bit stream and is otherwise occupied with blank bits, or in frequency division multiplexing, e.g. through the addition of sub-audio frequencies to the useful band. For network-wide modification of the key once it has become known, the address of the key memory SP is modified by the activation signal AS in the central station only (Fig.).
11 citations
TL;DR: In this paper, a laboratory system, transmitting 1 Gbit/s signals to a subscriber station and 565 Mbit/S signals back to a head station via one 20 km-long singlemode fiber, has been realized.
Abstract: A laboratory system, transmitting 1 Gbit/s signals to a subscriber station and 565 Mbit/s signals back to a head station via one 20 km-long single-mode fibre, has been realised. Wavelength division multiplexing via two 3 dB fibre couplers of selectivity 0.04 dB/nm has been used. The experiment demonstrates that bidirectional single-mode-fibre transmission is applicable to a future B-ISDN subscriber network.
6 citations
01 Apr 1984
TL;DR: In this paper, the authors demonstrate the significant advantages of TCM over FDM when used over narrowband radio systems which contain inherent nonlinearities, which can render FDM unusable for many applications, producing quite unacceptable levels of crosstalk.
Abstract: Time-compression multiplexing (TCM) is a spectrally efficient, time-domain multiplexing method, which is an alternative to the conventional and widely used frequency-division multiplexing technique (FDM). The paper demonstrates the significant advantages of TCM over FDM when used over narrowband radio systems which contain inherent nonlinearities. Indeed, these nonlinearities can render FDM unusable for many applications, producing quite unacceptable levels of crosstalk for an adequate signal/noise performance. TCM, however, is shown to overcome this problem without utilising excessive bandwidth, usually associated with time-domain multiplexing systems that employ digital modulation: for example, pulse code modulation. The paper contains details of the design and performance of a fully operational, two-channel TCM prototype, including a simple, yet robust, synchronisation system, which is then compared with an FDM system with an equivalent bandwidth.
5 citations
TL;DR: In this article, the use of junction current confinement high radiance light-emitting diodes for frequency division multiplexing of up to 14 analog television signals is examined by measuring cross modulation and composite triple beat.
Abstract: The use of junction current confinement high radiance light-emitting diodes for frequency division multiplexing of up to 14 analog television signals is examined by measuring cross modulation and composite triple beat. Fourteen channel transmission distance is limited to 0.3 km by chromatic and modal dispersion for typical 100-μm core graded index fiber. Most diodes were capable of 50-percent zero-to-peak current modulation depth at 80-mA drive before exceeding -48-dB cross-modulation (XMOD) distortion (2 channels). Increasing the number of channels decreases the distortion level for a fixed zero-to-peak current modulation depth.
3 citations
01 Aug 1984
TL;DR: In this paper, a low-loss access coupler with an asymmetric structure is presented, and manufacturing processes for the coupler are proposed, and low loss access couplers are used to avoid central control of the bus operation.
Abstract: A fiber optic data bus, using frequency division multiplexing (FDM) is discussed. The use of FDM is motivated by the need to avoid central control of the bus operation. A major difficulty of such a data bus is introduced by the couplers. An efficient low loss access coupler with an asymmetric structure is presented, and manufacturing processes for the coupler are proposed.
01 Jan 1984
TL;DR: In this article, the spectral occupancy of various amplitude modulated signals (DSB-SC, SSB-CC, conventional envelope modulation) in terms of the carrier and message spectrum is investigated.
Abstract: To describe how modulation enables a message to be matched to a band pass channel.
To show that amplitude modulation corresponds to multiplication of a message with a sinusoidal carrier.
To determine the spectral occupancy of various amplitude modulated signals (DSB-SC, SSB-SC, conventional envelope modulation) in terms of the carrier and message spectrum.
To explain how a message is recoverable from an AM signal using coherent detection.
To assess the influence of phase errors on coherent detection.
To show that angle (frequency or phase) modulation can be used to convey a message over a band pass channel.
To determine the spectral occupancy of a composite signal produced by frequency division multiplexing.
Patent•
16 May 1984
TL;DR: In this article, the authors proposed a method to record and reproduce signals as same as conventional one and execute the recording and reproducing of wide-band video signals by constituting in such a way that the video signal of a standard system and that in the wide band can be selectively recorded and reproduced.
Abstract: PURPOSE: To record and reproduce signals as same as conventional one and to execute the recording and reproducing of wide-band video signals by constituting in such a way that the video signal of a standard system and that in the wide band can be selectively recorded and reproduced. CONSTITUTION: A low-frequency conversion chroma signal in a narrow band from a chrominance signal recording processing circuit 3, an FM audio signal 15 and a pilot signal 16 are supplied to an adder 13, while a frequency multiplexing signal is recorded by a main video head 18. On the other hand, Y signal high frequency components in a high-frequency band and a high frequency line sequence chrominance signal are supplied to an adder 63, which becomes a multiplexed frequency signal, and recorded by subvideo head 70. Thus the high band Y signal can be obtained from the narrow band Y signal and high-frequency component of the Y signal at reproduction, and the video signal with high resolution can be obtained from the wide band Y signal and the wide band line sequence chrominance signal. COPYRIGHT: (C)1985,JPO&Japio
01 Jan 1984
TL;DR: A circuit to extract digital signaling information from its associated voice channel in frequency division multiplexing in metal gate CMOS technology will be presented.
Abstract: A circuit to extract digital signaling information from its associated voice channel in frequency division multiplexing will be presented. Frequency translation using switched capacitor techniques has been employed to achieve a 112 × 130mil2die in metal gate CMOS technology.
Patent•
21 Jun 1984
TL;DR: In this paper, the authors achieved radio line supervisory and control with high accuracy by transmitting a digital signal for control after applying the signal with frequency multiplexing extracting the control signal at a receiving side and transmitting the signal simultaneously with a voice signal for attining the control.
Abstract: PURPOSE:To attain radio line supervisory and control with high accuracy by transmitting a digital signal for control after applying the signal with frequency multiplexing extracting the control signal at a receiving side and transmitting the signal simultaneously with a voice signal for attining the control CONSTITUTION:Control information is coded into a control data and also into a correcting code at an error correcting coder 2 and they are transmitted A reproducing digital signal is decoded into the original control data at an error correcting code decoder 11 at a receiving side The decoder 11 generates and outputs a syndrome series, and also a control data and a clock pulse synchronized with the syndrome series A High probability measuring device 15 counts a pulse corresponding to a prescribed time length, its measured value is compared with a data Sref 17 being an estimated value of a prescribed voice transmission quality at a comparator 18, and when the measured value is larger, it is regarded as being deteriorated and the result is outputted to an estimated data output terminal 19 Thus, the radio line supervisoty control is attained with high accuracy
TL;DR: A technique relevant to SSM is described, in which specially constructed encoding sequences replace the ‘ almost orthogonal’ codes exclusively used in SSM systems, which results in a significant reduction in the bandwidth requirements for the same SNR.
Abstract: In a, multiplexing system the mutual interference between users is limited, by the use of either orthogonal functions such as in frequency division multiplexing (FD.M) and time division multiplexing (TDM) systems or ‘ almost orthogonal ’ codes such as in spread spectrum multiplexing (SSM) systems. The badnwidth required for the second ease is much wider than the one for the first case considering the same signal to noise ratio (SNR). In this paper, a technique relevant to SSM is described, in which specially constructed encoding sequences replace the ‘ almost orthogonal’ codes exclusively used in SSM systems. This results in a significant reduction in the bandwidth requirements for the same SNR. The corresponding multiplexing system has successfully been applied to the transmission of four voice channels via transceivers with X-mode facilities (16 kHz bandwidth), which normally can handle only one digital voice channel. The system is easier to work with these transceivers than other multiplexing systems (...
15 Aug 1984
TL;DR: A multi-function fibre-optic communication system has been constructed for carrying radar information from a radar head end to a remote display area using 1300nm led sources to reduce material dispersion.
Abstract: A multi-function fibre-optic communication system has been constructed for carrying radar information from a radar head end to a remote display area. High bandwidth video signals have been carried on FM subcarriers on a single fibre per channel basis. The radar video channels were a 20MHz analogue signal, a 10MHz analogue signal, and a 10MHz digital signal composite with a synchronising pulse. The aerial turning data was digitised and transmitted serially via a dedicated fibre with considerable capacity for additional information. Duplex speech and a TV video signal were transmitted over a single fibre using FDM and WDM. All the signals have been carried over a 3Km length of multimode optical cable using 1300nm led sources to reduce material dispersion. The WDM duplex link also used an 850nm led in the return direction.
13 Aug 1984
TL;DR: In this article, an incoherent imaging system based on frequency multiplexing is presented by using piezoelectric-elastoopticspace to frequency converter, where each image pixel at a different temporal frequency is converted into an electrical signal by using a single detector.
Abstract: An incoherent imaging system based on frequency multiplexing is presented. The concept was realized by using piezoelectric-elastoopticspace to frequency converter. By modulating each image pixel at a different temporal frequency, the entire image is converted into,an electrical signal by using a single detector. The spatial information of the original image is thus mapped into the frequency domain of an electrical signal. A one to one relation exists between the spatial frequency domain and the time domain, as well as between the spatial domain and the temporal frequency domains. This mapping allows one to perform spatial frequency manipulations in real time by processing the electrical signal. This multiplexing is obtained by using a two-dimensional array of piezoelectric-elastooptic light modulators. By using these two physical effects jointly, one gains the resonance characteristics of the piezoelectric crystal oscillator, together with the modulating properties of the elastooptic effect. Two schemes were studied and presented. The first is composed of two one-dimensional arrays, each composed of discrete crystals. The second one is based on a monolithic one-dimensional array, where a monolithic array is a piezoelectric wafer in which localized resonant domains are constructed.
19 Jun 1984
TL;DR: Injection locking of multiple semiconductor laser to a single master laser is a promising technique for increasing the amount of coherent optical power available from this highly efficient light source as mentioned in this paper, however, it makes the requirements of wavelength matching between the lasers and relative frequency stability more difficult to achieve.
Abstract: Injection locking of multiple semiconductor lasers to a single master laser is a promising technique for increasing the amount of coherent optical power available from this highly efficient light source. With FM sideband injection locking,1 the technique can also be used for frequency multiplexing for optical fiber communications and to generate narrowband microwave signals.2 Injection locking of a single semiconductor slave laser (SL) by a master laser (ML) has been extensively studied.3-4 Injection locking of many slave lasers, however, makes the requirements of wavelength matching between the lasers and relative frequency stability more difficult to achieve.