Showing papers on "Orthogonal frequency-division multiplexing published in 1990"

Optical heterodyne image-rejection receiver for high-density optical frequency division multiplexing system

Abstract: An optical heterodyne image-rejection receiver (IRR) for high-density optical frequency division multiplexing (OFDM) systems is described. The IRR was realized using balanced receivers, which showed more than 18-dB suppression over the 1.5-3.0-GHz IF region. Measured crosstalk penalties in a two-channel 560 Mb/s differential phase-shift keyed (DPSK) heterodyne optical communication system were realized for the first time. The crosstalk penalties in an OFDM system are estimated theoretically with and without the IRR. The required channel spacing and number of channels that can be accommodated in the 10-nm tuning range of the local laser are presented. A particular configuration of the IRR, its operation, and its performance limitations are discussed. The experimental results for image-rejection reception in a two-channel 560-Mb/s DPSK system are also given. Crosstalk penalties are estimated experimentally and compared to the theoretical calculation. Since the conventional configurations of the IRR are very sensitive to the polarization fluctuation of the transmitted signals, polarization-insensitive IRRs are proposed and their features are considered. >

Broadband information distribution networks employing optical frequency division multiplexing technologies

Abstract: The authors consider the configuration of the OFDM (optical frequency division multiplexing) broadband distribution networks, including the communication service, and discuss the following OFDM technologies: a multichannel frequency stabilization technique, a polarization-insensitive waveguide FS-SW (frequency selection switch), and an FSK (frequency-shift keying)/direct-detection scheme using a Mach-Zehnder filter. The waveguide FS-SW, consisting of seven Mach-Zender filters, successfully selected channels with a total crosstalk of less than -13 dB. The balanced receiver configuration of the OFD (optical frequency discriminator) receiver is 3 dB more sensitive than single-detection-type OFDs, such as a Fabry-Perot-filter-type discriminator. A 100-channel OFDM transmission/distribution experiment at 622 Mb/s over a 50 km fiber length was performed. >

A proposal of time-division, time-compressed multiplexing FM mobile radio system

Abstract: A TDMA (time-division multiple access) system which adopts the TCM (time-compression multiplexing) technique is proposed for application to cellular systems. The significant advantages of the TCM over the FDM (frequency-division multiplexing) system when used in the narrowband single channel per carrier are demonstrated with respect to the frequency spectrum efficiency. The intention is to develop a communication format that would be applicable to cellular systems. The application of the time-compression technique to analog signals is fused with the digital technique, and thus a modulation format of cellular or microcell systems that maintains the advantages of analog systems is developed. >

10-Gbit/s optical transmitter module with multiquantum well DFB LD and doped-channel hetero-MISFET driver IC

Abstract: Long haul optical transmission systems to handle ~10-Gbit/s signals are now being developed.1·2 For such large capacity transmission systems, a high speed laser diode (LD) driver IC is a key component.3 The i-AlGaAs/n-GaAs doped-channel hetero-MIS- FETs (DMTs), taking advantage of high current drivability and high breakdown voltage, are attractive for high output power ICs, such as LD drivers.4 We have constructed miniature optical transmitter modules using the newly developed DMT LD driver ICs and high speed multiquantum well (MQW) DFB LDs. Very high speed operation, up to 10 Gbit/s, has been achieved.