We have investigated the use of uncooled and unisolated 1.3 mu m DFB lasers in a QPSK transmission system. Our measurements include both BER measurements and detailed analog tests on two commercial DFB lasers in cylindrical packages. Error-free transmission was observed even in the presence of back reflections as large as -8 dB. The laser relative intensity noise (RIN) was measured as a function of temperature and back reflection. The change in RIN in the temperature range -10 degrees C to +60 degrees C was less than that due to back reflections, suggesting that error-free QPSK transmission can be acheived over a large temperature range with these DFB lasers

Summary form only given. In summary, by deploying low-cost mini fiber nodes (mFNs) deep into coax distribution networks, the mFN-based hybrid fiber coaxial (HFC) evolution strategy provides a novel solution to upstream limitations in traditional HFC networks with further enhanced system bandwidth even beyond the limits of coax amplifiers. This results in a transparent HFC upgrade for high capacity without incurring the cost of system re-design and re-engineering.

In this letter, we present a subcarrier-multiplexed passive-optical network (SCM-PON) which transmits upconverted 16-CAP [1] signals to the curb, Once these RF channels are down-converted to their original 16-CAP format they are capable of being transmitted over unshielded-twisted-pair copper wires (UTP) to the home. This enables a very inexpensive drop to be made from the ONU to the home, A BER< 10(-9) over optical fiber has been achieved, This is the first demonstration of upconverted 16-CAP transmission.

Summary form only given. In conclusion, we have demonstrated that out-of-band clipping tones can be used to reduce optical beat interference (OBI), and give error-free transmission of QPSK signals. To perform this experiment we used a self-homodyne technique. This technique provides a simple way to simulate worst-case OBI without relying on matching lasers.

We present a method for improving the performance of a subcarrier multiplexed passive optical network (SCM-PON) in the presence of optical beat interference (OBI), By introducing strong ''clipping tones'' (optical-modulation depth > 1) on each of the lasers their optical spectrum can be broadened, thereby ameliorating the effects of OBI. By carefully selecting the RF band used to carry signals, and that used for ''clipping tones,'' OBI can be reduced without the clipping inducing errors, We have demonstrated the effectiveness of this technique by measuring the BER of a QPSK channel in the presence of OBI, A delayed self-homodyne technique was used to simulate worst-case conditions.

We present an optical-data link that uses the simplest possible optical components-a laser at each end serves as both the light source and detector. A laser cannot transmit and detect light simultaneously, therefore, we use low-duty-cycle pulses, where one laser derives its clock from the signal it receives from the other laser. By interweaving the bits, and careful choice of pulse length, each laser is able to separate transmitted from received signals. We have transmitted 1 Mb/s data over 12 km of fiber with a BER<10/sup -9/. To our knowledge, this "proof of concept" demonstration is the first to use commercial Fabry-Perot lasers as transceivers in a full-duplex system.< >

We investigate the use of uncooled lasers in an optical fiber transmission system employing quadrature-phase-shift keyed (QPSK) signals on subcarriers. The BER of a 2 Mb/s QPSK channel is measured in a system containing 60 subcarriers. Error-free performance (BER <10/sup -9/) is achieved over a wide range of modulation depths. This demonstrates that these inexpensive lasers can be used in multi-channel digital systems.< >

We demonstrate the first broad-band AM-VSB/64 QAM cable TV

In order to utilize the 1GHz bandwidth made available with cable systems based on fiber-trunk/coax-distribution architecture, we have built and evaluated the first broadband AM-VSB/64QAM hybrid lightwave CATV system which can provide 60 conventional AM-VSB channels (55.25MHz – 439.25MHz) and ten 64QAM (90Mb/s/ch) channels (525MHz – 750MHz) using a single DFB laser. This system is compatible with current cable networks and promises delivery of new digital services using video compression and spectrally efficient multi-level RF techniques. The channel capacity can be increased greatly with little increase in laser’s overall RF load, making one-laser/one-fiber broadband transmission feasible and attractive[1,2].

Analog subcarrier-multiplexed lightwave systems that carry 40- 80 AM-virtual-sideband (AM-VSB) channels have become established for transmission of the cable-television signal.1 Increasingly, applications that include a mix of channel types, AM-VSB and digital or quadrature amplitude modulation (QAM), are being considered. A large amount of polarizationmode dispersion (PMD) in the lightwave path has been seen to adversely affect the performance of AM-VSB systems by generating second-order distortion.2,3 Will a QAM channel transmitted over a lightwave link with large PMD also be degraded? We measured the performance of a 64-QAM channel as a function of the second-order distortion introduced by PMD in the lightwave transmission path. The degradation in the bit error rate (BER) was compared to that caused by noise and by distortion from other sources.

We demonstrate that the impulse noise generated from clipping AM signals limits QAM bit-error performance in AM-VSB/M-QAM hybrid optical transmission systems. A new technique is developed to adequately predict QAM bit-error rate by defining a measurable parameter which can be obtained from impulse counting using a standard spectrum analyzer.

AM-virtual-sideband/M-ary quadrature-amplitude-modulation (AM-VSB/M-QAM) hybrid optical transmission has been shown to be a very promising technique for allowing the CATV' industry to use the I-GHz bandwidth made available with systems based on liber feeders.1-3 Traditional AM-VSB channels (55.25-439.25 MHz are provided, and new digital services can be delivered in the high-frequency band (500 MHz to 1 GHz by using multilevel of techniques. However, recent studies have demonstrated that the interference from the AM band can cause serious impairment in QAM bit-error performance.2,3 The QAM bit-error probability can be increased greatly by AM interference, regardless of the QAM signal level. In this paper we confirm that this bit-error impairment is caused entirely by clipping-induced impulse noise, as shown in Fig. 1. Furthermore, we define a new parameter that can be measured on a spectrum analyzer and used to predict QAM bit-error characteristics.