JAN/ FE B 20 13 9 ® ROBERT BLUM is product marketing director at Oclaro . FEATURE By ROBERT BLUM The groundwork has been laid to develop integrated components that will reduce the cost and power consumption of future 100- Gbps systems. Wavelength ( nm) Lorentzian linewidth ( MHz) 1575 1565 1555 1545 1535 1525 0.0 0.1 0.2 0.3 0.4 0.5 FIGURE 1. Low phase noise micro- ITLA module ( left) and its Lorentzian linewidth ( right). Integration enables new 100G metro/ long haul coherent pluggable transceivers T HE PAST YEAR HAS SEEN remarkable growth in the deployment of coherent 100G DWDM systems, with about 10,000 total ports shipped into the core optical network. In 2013, these volumes are forecast to more than double, and the rapid growth rate is expected to continue into next year. Expectations are that some 60,000 coherent 100G ports will ship in 2014. What’s enabling the success of coherent 100G from a technical perspective? On the one hand, various DSP engines and other electronic components ( such as modulator drivers or transimpedance amplifiers – TIAs) have now become available with new variants under development that have been tailored for low power dissipation and less demanding applications in the metro space. On the other hand, significant progress has been made on the optical side. Lithium niobate ( LiNbO 3 ) modulators are available with low insertion loss and high bandwidth to support polarization- multiplexed quadrature phase- shift keying ( PM- QPSK), and tunable lasers with low phase noise and narrow linewidth are starting to reach cost points similar to those in 10G applications. In addition, coherent receivers have become widely available in the industry. In a way, these first generation deployments have also benefited from the successful standardization of these key optical components through OIF implementation agreements. But similar to what has happened in the 10G market, we expect that a different set of optical components will dominate the second and third generation of coherent 100G deployments, where power dissipation, density, and cost are key. Only highly integrated components will be able to meet the challenging requirements of the high- volume metro and regional- network market, specifically when it comes to providing 100G coherent functionality in a pluggable form factor such as a digital CFP or an analog CFP2. We’ll discuss how photonic integration based on indium phosphide