100-Gb/s dense wavelength division multiplexed (DWDM) transmitter and receiver photonic integrated circuits (PICs) are demonstrated. The transmitter is realized through the integration of over 50 discrete functions onto a single monolithic InP chip. The resultant DWDM PICs are capable of simultaneously transmitting and receiving ten wavelengths at 10 Gb/s on a DWDM wavelength grid. Optical system performance results across a representative DWDM long-haul link are presented for a next-generation optical transport system using these large-scale PICs. The large-scale PIC enables significant reductions in cost, packaging complexity, size, fiber coupling, and power consumption.

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Large-scale photonic integrated circuits

The two main trends in the progress of ultrawide-band/high-frequency photodetectors (PD's), improving the bandwidth-efficiency product and obtaining a high saturation current, are reviewed. With respect to achieving large bandwidth-efficiency, the limiting factors and potentials of edge-coupled (waveguide, waveguide-fed, traveling-wave, periodic-traveling-wave), resonant-cavity, and refracting-facet photodiodes, as well as the avalanche photodiode are discussed. Regarding high-saturation current, the author estimated how much the space-charge effect limits the saturation current and two ways to reduce the space-charge effect are outlined. One way is to distribute the photocarriers along the edge-coupled PD's and the other is to increase the carrier velocity using a uni-traveling carrier structure. The waveguide-photodiode-based technologies that we have developed are also presented; namely the design and fabrication of a 100-GHz waveguide photodiode (WGPD), uni-traveling carrier WGPD, 60-GHz packaging, and a 20-GHz large-core WGPD for planar lightwave circuit integration. A 50-Gb/s receiver opto-electronic integrated circuit technology based on the WGPD is also presented.

Ultrawide-band/high-frequency photodetectors

Photonic packet switches offer high speed, data rate and format transparency, and flexibility required by future computer communications and cell-based telecommunications networks. In this paper, we review experimental progress in state-of-the-art photonic packet switches with an emphasis on all-optical guided-wave systems. The term all-optical implies that the data portion of a packet remains in optical format from the source to the destination. While the data remain all-optical, both optical and optoelectronic techniques have been used to process packet routing functions based on extremely simple routing protocols. An overview of the design issues for all-optical photonic packet switching is given and contrasted with electronic packet switch implementations. Low-level functions that have been experimentally implemented include routing, contention resolution, synchronization, and header regeneration. System level demonstrations, including centralized photonic switching and distributed all-optical multihop networks, will be reviewed. >

Photonic packet switches: architectures and experimental implementations

For high-bit-rate long-haul fiber optic communications, the avalanche photodiode (APD) is frequently the photodetector of choice owing to its internal gain, which provides a sensitivity margin relative to PIN photodiodes. APDs can achieve 5-10-dB better sensitivity than PINs, provided that the multiplication noise is low and the gain-bandwidth product is sufficiently high. In the past decade, the performance of APDs for optical fiber communication systems has improved as a result of improvements in materials and the development of advanced device structures. This paper presents a brief review of APD fundamentals and describes some of the significant advances

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Recent Advances in Telecommunications Avalanche Photodiodes

The development of high-performance optical receivers has been a primary driving force for research on III-V compound avalanche photodiodes (APDs). The evolution of fiber optic systems toward higher bit rates has pushed APD performance toward higher bandwidths, lower noise, and higher gain-bandwidth products. Utilizing thin multiplication regions has reduced the excess noise. Further noise reduction has been demonstrated by incorporating new materials and impact ionization engineering with beneficially designed heterostructures. High gain-bandwidth products have been achieved waveguide structures. Recently, imaging and sensing applications have spurred interest in low noise APDs in the infrared and the UV as well as large area APDs and arrays. This paper reviews some of the recent progress in APD technology.

Recent advances in avalanche photodiodes

Monolithic photoreceivers, using the base-collector junction of an InP/InGaAs phototransistor structure for a p-i-n photodetector, have been fabricated for the first time. Bandwidths as high as 3 GHz and bit rates as high as 5 Gb/s, with sensitivities of -22.5 dBm and -21.5 dBm for light focused on the p-i-n or on the first stage transistor of the preamplifier, respectively, have been achieved. These results represent the highest operating speed demonstrated for any phototransistor-based receiver. >

High-speed monolithic p-i-n/HBT and HPT/HBT photoreceivers implemented with simple phototransistor structure

Measurements of InP/InGaAsP/InGaAs separate absorption, grading, and multiplication avalanche photodiode multiplication indicate that at high gains the excess noise factors approach values predicted by the conventional continuum theory. However, at lower gains the noise is suppressed. This is probably an artifact of the very thin multiplication layers which have been used to increase the gain-bandwidth product. From the frequency response of the noise power, a gain-bandwidth product of 60 GHz, which is consistent with the value of 57 GHz obtained directly from bandwidth measurements, is deduced. >

Multiplication noise of wide-bandwidth InP/InGaAsP/InGaAs avalanche photodiodes

Metal organic molecular beam epitaxy (MOMBE) was successfully used for the first time to realise a high speed monolithic photoreceiver. Incorporating an InGaAs pin photodetector followed by a transimpedance preamplifier circuit implemented with InP/InGaAs heterojunction bipolar transistors (HBTs), the OEIC photoreceiver had a bandwidth of 6 GHz and a midband transimpedance of 350 ω. In a system experiment performed at 10 Gbit/s, the receiver exhibited a sensitivity of –15.5 dBm for a bit error rate of 10-9 at a wavelength of 1.53 μm. This is the first demonstration of operation of a long wavelength OEIC photoreceiver at this speed.

A 10 Gbit/s OEIC photoreceiver using InP/InGaAs heterojunction bipolar transistors

Heterojunction bipolar transistors have been monolithically integrated with a pin photodetector to realise a high speed transimpedance photoreceiver. The OEIC, made from MOVPE-growth InP/InGaAs heterostructures, had a bandwidth of 2.8 GHz with a transimpedance of 750 Ω. It was successfully operated at 4 Gbit/s with a sensitivity of −21 dBm at a wavelength of 1.5 μm.

4 Gbit/s pin/HBT monolithic photoreceiver

An InGaAs photodetector for detection in the 1.0?1.5?m wavelength range has been integrated at the end of and above a ridge waveguide in InP. The waveguides were in n?-InP/n+-InP and had an average propagation loss of 3dB/cm at 1.15?m. The reflection losses were 3dB and the coupling loss was 2dB. The photodetector was an InGaAs photoconductor lattice-matched to InP and exhibited a bias-dependent optical gain of up to 2.5 with a unity-gain quantum efficiency of 49% at 1.15?m. 25% of the guided light was absorbed by the photoconductor. The speed of the photoconductor was found to be bias-dependent, varying from 10 ns to 150 ns rise/fall times.

G.J. Qua

Papers

High-speed monolithic p-i-n/HBT and HPT/HBT photoreceivers implemented with simple phototransistor structure

Multiplication noise of wide-bandwidth InP/InGaAsP/InGaAs avalanche photodiodes

A 10 Gbit/s OEIC photoreceiver using InP/InGaAs heterojunction bipolar transistors

4 Gbit/s pin/HBT monolithic photoreceiver

Monolithic integrated waveguide photodetector