Randal A. Salvatore

Large-scale photonic integrated circuits

We present an overview of Infineras current generation of 100 Gb/s transmitter and receiver PICs as well as results from the next-generation 500 Gb/s PM-QPSK PICs.

InP Photonic Integrated Circuits

InP is an ideal integration platform for optical generation, switching, and detection components operating in the range of 1.3-1.6 m wavelength, which is preferred for data transmission in the most prevalent silica-based optical fiber. We review the current state of the art in advanced InP photonic ICs.

Current Status of Large-Scale InP Photonic Integrated Circuits

In this paper, the current state of the art for large-scale InP photonic integrated circuits (PICs) is reviewed with a focus on the devices and technologies that are driving the commercial scaling of highly integrated devices. Specifically, the performance, reliability, and manufacturability of commercial 100-Gb/s dense wavelength-division-multiplexed transmitter and receiver PICs are reviewed as well as next- and future-generation devices (500 Gb/s and beyond). The large-scale PIC enables significant reductions in cost, packaging complexity, size, fiber coupling, and power consumption which have enabled benefits at the component and system level.

Electroabsorption modulated laser for long transmission spans

Strain-compensated AlGaInAs quantum-well electroabsorption modulated lasers (EMLs) transmit at 10 Gbits/s on uncompensated transmission spans of >75 km of standard fiber and >225 km of MetroCor fiber. Details of the design, fabrication, and testing are presented. A complex-coupled distributed feedback (DFB) grating is used to enable high output power. The epitaxy and chip structure are described. The paper studies what is needed to accomplish long-span transmission in terms of minimum physical requirements for laser mode control, facet reflection, index grating strength, laser-modulator matching, laser-modulator electrical isolation, modulator extinction ratio, modulator capacitance, linewidth enhancement factor, etc. The interaction of the modulator with the laser is analyzed and a requirement for this structure is computed for the electrical isolation resistance between modulator and laser contacts. Stability of the laser source is discussed and a method is derived for determining the gratings gain-coupling coefficient at operating power. Chirp due to the modulator is analyzed. Nonzero chirp of the modulator is shown to have beneficial impact on the quality of the signal after transmission. The effect of a bias-dependent alpha parameter is analyzed. Because bit-error rate is a strong function of mean alpha parameter and not a strong function of the range of alpha during nonreturn-to-zero modulation, we determine that tuning the chirp of the EML modulator to suit different fiber types (MetroCor, SMF-28, etc.) is practical. Specific tradeoffs are also required. Experimental results verify the analysis.

Large-Scale InP Transmitter PICs for PM-DQPSK Fiber Transmission Systems

We report here the first demonstration of a large-scale monolithically integrated InP-based 10-channel 45.6-Gb/s per channel transmitter photonic integrated circuit employing polarization-multiplexed differential quadrature phase-shift keying modulation format.

Effect of noise on the power spectrum of passively mode-locked lasers

We analyze the effects of noise on the power spectrum of pulse trains generated by a continuously operating passively mode-locked laser. The shape of the different harmonics of the power spectrum is calculated in the presence of correlated timing fluctuations between neighboring pulses and in the presence of amplitude fluctuations. The spectra at the different harmonics are influenced mainly by the nonstationary timing-jitter fluctuations; amplitude fluctuations slightly modify the spectral tails. Estimation of the coupling term between the longitudinal cavity modes or the effective saturable absorber coefficient is made from the timing-jitter correlation time. Experimental results from an external cavity two-section semiconductor laser are given. The results show timing-jitter fluctuations having a relaxation time much longer than the repetition period.

Large-scale photonic integrated circuits for long-haul transmission and switching

Feature Issue on Nanoscale Integrated Photonics for Optical Networks Dense wavelength division multiplexed (DWDM) large-scale, single-chip transmitter and receiver photonic integrated circuits (PICs), each capable of operating at 100 Gbits/s, have been deployed in the field since the end of 2004. These highly integrated InP chips have significantly changed the economics of long-haul optical transport networks. First, a review of the ten-channel, 100 Gbits/s PIC is presented. Then two extensions of the technology are demonstrated; first is wide temperature, coolerless operation of the 100 Gbits/s PIC, and second is a single integrated chip with 40 channels operating at 40 Gbits/s, capable of an aggregate data rate of 1.6 Tbits/s.

Multi-channel coherent PM-QPSK InP transmitter photonic integrated circuit (PIC) operating at 112 Gb/s per wavelength

A 10-wavelength, polarization-multiplexed, monolithically integrated InP transmitter PIC is demonstrated for the first time to operate at 112 Gb/s per wavelength with a coherent receiver PIC.

Noise characterization of a pulse train generated by actively mode-locked lasers

We analyze the entire power spectrum of pulse trains generated by a continuously operating actively mode-locked laser in the presence of noise. We consider the effect of amplitude, pulse-shape, and timing-jitter fluctuations that are characterized by stationary processes. Effects of correlations between different parameters of these fluctuations are studied also. The nonstationary timing-jitter fluctuations of passively mode-locked lasers and their influence on the power spectrum is discussed as well.

From Visible Light-Emitting Diodes to Large-Scale III–V Photonic Integrated Circuits

The discovery of the visible light-emitting diode (LED) 50 years ago by Holonyak and Bevacqua and the associated demonstration of the viability of the III-V semiconductor alloy created a foundational basis for the field of optoelectronics. Key advances which enabled the progression from the first visible LED to todays III-V photonic integrated circuits (PICs) are described. Furthermore, the current state-of-the-art 500-Gb/s and 1-Tb/s large-scale InP transmitter and receiver PICs and their essential role in the optical communications networks are reviewed.