High-sensitivity receiver optical preamplifiers

High-receiver sensitivities of -40.9, -44.3, -46.2, -49.0, and -51.3 dBm are reported at 2.4, 1.8, 1.2, 0.62, and 0.14 Gb/s, respectively, using a low-noise, 980-nm diode-pumped, erbium fiber amplifier in the receiver preamplifier configuration with all field usable components. This corresponds to a best sensitivity of 156 photons/bit at the input of the optical amplifier (96 photons/bit at the input of the erbium-doped fiber). Selection of a low-chirp laser-diode transmitter, an optical filter with a bandwidth appropriate for filtering the signal, and a low-noise electrical amplifier with appropriate bandwidth in the post detection stage are all critical to achieve very high-receiver sensitivities     

560 Mb/s optical PSK synchronous heterodyne experiment

A phase-locked optical heterodyne receiver constructed using a 1320-nm diode-pumped miniature Nd:YAG ring laser is discussed. Using this receiver and a transmitter based on another Nd:YAG laser, a 560-Mb/s phase-shift keying (PSK) synchronous heterodyne transmission was demonstrated over 78 km of single-mode fiber. With an optical phase-locked loop (PLL) natural frequency of 32 kHz and a damping factor of 1.46, the receiver sensitivity, measured at the output of the transmission link, was -48.7 dBm, or 159 photons/b. The corresponding detected sensitivity, measured on the surface of the p-i-n diode, was -51.8 dBm or 78 photons/b. This result suggests that the receiver sensitivity would have been about 82 photons/b if a balanced receiver with 0.2-dB excess coupler loss had been used. The impact of the finite intermediate frequency (IF) on heterodyne system performance was investigated; it was found that an IF of at least twice the bit rate is needed for a negligibly small penalty     

Low-noise optical receiver for high-speed optical transmission

This paper describes the design of a low-noise optical receiver using Si bipolar transistors for high-speed optical transmission. The conventional common emitter-common collector circuit (CE-CC pair) and Darlingtou circuit (transimpedance amplifiers with parallel feedback) are studied. Optimal CE-CC pair collector-biasing current for attaining minimum noise current with a 400-MHz bandwidth is 2.7 mA, and less than 1.2 mA for the Darlington circuit. It is confirmed that the Darlington circuit is better than the CE-CC pair in signal-to-noise ratio by about 1.5 dB. The low-noise Darlington optical receiver with a Ge-avalanche photodiode has achieved an optical sensitivity of -41 dBm for a 400 Mbit/s RZ pulse with a bit error rate of 10^-10. This is a 2.5-dB improvement in optical sensitivity over that of the conventional CE-CC receiver.     

Chameleon: a dual-mode 802.11b/Bluetooth receiver system design

In this paper, an approach to map the Bluetooth and 802.11b standards specifications into an architecture and specifications for the building blocks of a dual-mode direct conversion receiver is proposed. The design procedure focuses on optimizing the performance in each operating mode while attaining an efficient dual-standard solution. The impact of the expected receiver nonidealities and the characteristics of each building block are evaluated through bit-error-rate simulations. The proposed receiver design is verified through a fully integrated implementation from low-noise amplifier to analog-to-digital converter using IBM 0.25-/spl mu/m BiCMOS technology. Experimental results from the integrated prototype meet the specifications from both standards and are in good agreement with the target sensitivity.     

Evaluation of Sensitivity of the Digital Coherent Receiver

In this paper, we investigate the sensitivity of the digital coherent receiver both theoretically and experimentally. The receiver sensitivity close to the shot-noise limit is demonstrated in the 10-Gbit/s binary phase-shift keying system with the help of a low-noise optical preamplifier. We also introduce polarization diversity into our receiver. Maximal-ratio polarization combining in the digital domain makes the receiver sensitivity independent of the state of polarization of the incoming signal without power penalty.      

Coherent optical QPSK intradyne system: concept and digitalreceiver realization

A receiver concept based on optical quadrature phase-shift keying (QPSK) and a digital realization of synchronous demodulation including phase synchronization is presented. To keep the signal processing bandwidth low a phase diversity receiver, called an intradyne receiver, with an orthogonal electrical demodulation is proposed. Basic principles of the synchronous orthogonal and digital demodulation are described. After the evaluation of the shot noise limit some aspects of the digital phase-locked loop (PLL) are presented. In a 100-Mb/s transmission system a receiver sensitivity of -51.6 dBm has been measured. The loss in relation to the shot noise limit of -66.3 dBm (18 photons/b) is mostly due to the low local laser power and the influence of the receiver input noise     

Low-noise optical receiver for high-speed optical transmission

This paper describes the design of a low-noise optical receiver using Si bipolar transistors for high-speed optical transmission. The conventional common emitter-common collector circuit (CE-CC pair) and Darlington circuit (transimpedance amplifiers with parallel feedback) are studied. Optimal CE-CC pair collector-biasing current for attaining minimum noise current with a 400-MHz bandwidth is 2.7 mA, and less than 1.2 mA for the Darlington circuit. It is confirmed that the Darlington circuit is better than the CE-CC pair in signal-to-noise ratio by about 1.5 dB. The low-noise Darlington optical receiver with a Ge-avalanche photodiode has achieved an optical sensitiyity of -41 dBm for a 400 Mbit/s RZ pulse with a bit error rate of 10^-10. This is a 2.5-dB improvement in optical sensitivity over that of the conventional CE-CC receiver.     

Receiver design for high-speed optical-fiber systems

The technology of optical-fiber systems is advancing rapidly. Parallel to the development of long-haul telecommunication systems in the gigabits per second data rates operating in the long-wavelength region is the wide penetration of optical-fiber systems in local area networks, video trunking and distribution, sensors, etc. These diversified applications impose different and often conflicting constraints on the optical receiver. This paper re-examines the optical receiver design in view of these different requirements, namely, high receiver sensitivity, wide dynamic range, transparent to the operating bit rate, unrestricted data format, and fast acquisition time. Design tradeoffs between conflicting receiver requirements are considered in detail. In particular, the sensitivity of high-capacity long-wavelength transmission systems is emphasized. The state-of-the-art performance of photodetectors and low-noise amplifiers is discussed. We show that dark current of avalanche photodiodes (APD's) is the main factor limiting the sensitivity of long-wavelength optical receivers. In addition, as an example, we report on the design and experimental performance of a hybridized low-noise optical receiver amplifier capable of more than 2-Gbits/s operation. The input noise spectral density achieved is 9 pA/sqrt{Hz}with a noise corner frequency of 920 MHz, corresponding to an equivalent noise resistance of 120 Ω.     

Optical phase-locked PSK heterodyne experiment at 4 Gb/s

A 4 Gb/s phase-locked optical PSK (phase shift keying) heterodyne communication system is demonstrated. The receiver was implemented with a single 100-Ω loaded p-i-n photodiode and a 1320-nm diode-pumped miniature Nd:YAG laser as a local oscillator. For a 2⁷-1 PRBS (pseudorandom bit sequence), the receiver sensitivity was -34.2 dBm or 631 photons/bit. The corresponding power on the surface of the detector was -37.3 dBm or 309 photons/bit. With a 2¹⁵-1 PRBS, a 2.6 dB additional sensitivity degradation was observed due to the nonideal frequency response of the phase modulator and the receiver amplifiers     

Noise performance of erbium-doped fiber amplifier pumped at 1.49μm, and application to signal preamplification at 1.8 Gbit/s

Direct measurements of the noise figure of an erbium-doped fiber amplifier are described. With an amplifier gain as high as 36 dB, a noise figure as low as 4.1 dB was measured. Noise figures remained below 6 dB for signal wavelengths within the high gain (G>20 dB) region of the amplifier. An optical receiver sensitivity of -43 dBm at 1.8 Gb/s, corresponding to 215 photons/b, was achieved using the fiber amplifier as an optical preamplifier for a direct detection receiver     

4-Gb/s PSK homodyne transmission system using phase-lockedsemiconductor lasers

Homodyne detection of 4-Gb/s pilot-carrier binary-phase-shift-keyed (BPSK) optical signals using external-cavity semiconductor lasers synchronized by a linear phase-locked loop is discussed. A 2¹⁵-1 pseudorandom binary sequence (PRBS) has been transmitted through a short fiber with a receiver sensitivity of -44.2 dBm or 72 photons/bit. After transmission through 167 km of standard single-mode fiber, the sensitivity is -43.6 dBm or 83 photons/bit. A balanced PIN/HEMT transimpedance receiver which has a 3-dB bandwidth from 100 kHz to 10.1 GHz and an average equivalent input noise current of 10.8 pA/√Hz is used     

Sensitivity of optically preamplified DPSK receivers withFabry-Perot filters

The error-rate performance of a DPSK lightwave receiver having an optical amplifier followed by a Fabry-Perot filter and delay-line demodulator is analyzed. Receivers with sampling and with integrate-and-dump threshold comparison are compared to the well-known result for a matched optical filter. The Fabry-Perot filter decreases the sensitivity at 10^-9 error-rate from 20 to 24.5 photons/b with optimum optical filter bandwidth and postdetection integration time     

High-performance balanced dual-detector GaAs IC receiver for 565 Mbit/s optical heterodyne detection

A high-performance balanced dual-detector receiver which uses a low-noise GaAs IC transimpedance preamplifier has been developed for a 565 Mbit/s optical fibre DPSK heterodyne system. This receiver has achieved the highest sensitivity reported at this bit rate: -51-9 dBm.<>     

High-sensitivity semiconductor optically preamplified Q-PPM receiver

An optically preamplified receiver for 980-nm laser intersatellite communications is reported. A record sensitivity of 330 photons/bit for a semiconductor optically preamplified receiver is obtained at 50 Mb/s with quaternary pulse-position-modulation (Q-PPM). The experimental results are shown to be in excellent agreement with a novel exact calculation of the optically preamplified receiver Q-PPM bit-error rate (BER). Calculated performance based on these results shows that with an improved optical transmitter the receiver attains 1.5 dB higher sensitivity than previously achieved at this wavelength.     

Theory of direct-detection lightwave receivers using opticalamplifiers

A simple theory is presented for analyzing the sensitivity and bit-error rate (BER) performance of direct-detection lightwave receivers using optical amplifiers. The analysis provides closed-form expressions for the BER and receiver sensitivity, and includes the impact of phase noise. Furthermore, the proposed theory predicts the optimum filter bandwidth values required for linewidths of practical interest (up to 100% of the bit rate). For the special case of zero linewidth, the average signal energy predicted by this work is 42.3 photons/b at BER=10 ^-9. This result is within 0.47 dB of the sensitivity predicted by more accurate techniques     

High-performance dense FDM coherent optical network

The results obtained with a densely spaced frequency division multiplexing (FDM) optical star network providing random channel selection by a digitally tuned high-sensitivity heterodyne receiver are presented. The experimental system consists of six 200-Mb/s frequency-shift keyed (FSK) modulated channels, spaced by 2.2 GHz and multiplexed by a star coupler. Channel selection is performed by a computer-controlled random-access heterodyne receiver having a sensitivity of 74 photons/b at a BER of 10^-9, which is 1.7 dB from the quantum limit. The digital-tuning random-access capability (which depends on the frequency-tuning current relationship of the local oscillator (LO) laser) is protected against frequency drifts of the LO laser. The receiver can also detect the absence of a selected channel. In this case, the receiver locks to the next available channel and displays which channel is received instead. The results obtained indicate that this system has potential throughput of 2000 Gb/s     

Low-noise optical detection of a 1.1 Gb/s optical data stream

A low-noise, 1.1 Gb/s optical receiver has been built using a silicon a.p.d. and a GaAs f.e.t. The receiver sensitivity was evaluated using error-rate measurements, and for a bit error rate of 10?9, with no fibre, the measured optical sensitivity was ?37.0 dBm. These results are used as a basis for the calculation of maximum repeater spacings for 1.1 Gb/s systems operating at 0.85 ?m and 1.25 ?m wavelengths.     

Communications performance of a multimode EDFA

We report an investigation of a multimode EDFA used as an optically preamplified receiver. A two-stage amplifier pumped at 982 nm shows gain of up to 40 dB at 1553 nm. We study the communications performance of the receiver at 10 Gb/s and compare it with theory. The measured sensitivity is 220 photons per bit at a bit error rate of 10/sup -9/ and data rate of 10 Gb/s. This is 4.5 dB from the quantum limit of 75 photons per bit for a 56 mode amplifier.     

Low-Noise Millimeter-Wave Receivers

Over the past several years, significant improvements have been made in solid-state devices (that is, avalanche diodes, Gunn diodes, varactors, mixer diodes, etc.) that have enhanced the overall capability and low-noise performance of millimeter-wave receivers. With these improved devices, it is now possible to configure completely solid-state low-noise millimeter-wave receivers. As is similar in the microwave region, low-noise parametric amplifiers, broad-band low-conversion-loss mixers, and solid-state local oscillators are now available. Furthermore, cryogenically cooled parametric amplifiers and mixers are also being developed that will result in achieving the ultimate in system sensitivity. With the flexibility offered by these completely solid-state millimeter-wave components, it is now possible to design the optimum system configuration for the intended application whether it be an advanced communication system, a sophisticated EW application, a RADAR system, a radiometric system, or satisfying any of the numerous receiver requirements that are being evolved. This paper explores the trends that are being developed in the millimeter-wave region and their application to system design. The performance criterion of various receiver systems and their sensitivity requirements are presented. A review of the system operating noise temperature concept and the method by which it can be determined and its applicability to low-noise components is demonstrated. A review of the state-of-the-art of low-noise systems and experimental data obtained in the millimeter-wave region is also presented.     

Receiver Design for Digital Fiber Optic Transmission Systems Using Manchester (Biphase) Coding

An analysis of the sensitivity of an optical receiver in a digital communication system using Manchester (biphase) coding is performed. Both cases of p-i-n and avalanche photodiodes are considered. Experimental results for the sensitivity of a Manchester receiver operating at 250 Mbits/s are reported. Two types of low noise receiver amplifiers, namely the high impedance and the transimpedance amplifier, are designed and implemented for use in the receiver. A receiver sensitivity of -49.8 dBm in terms of detected optical power is obtained (at a 10^-9bit error rate and 0.1 laser extinction ratio), which corresponds to only 175 average photons per bit. It is shown that in contrast to the NRZ code, the Gaussian approximation theory tends to underestimate the Manchester receiver sensitivity. Tradeoffs between Manchester and NRZ coding are also discussed in terms of receiver sensitivity and ease of implementation. It is shown that Manchester coding is an attractive alternative to NRZ coding for optical transmission systems, particularly when an avalanche photodiode is used.