Metro and Data Center Optical Networks and Short-Reach Links V

The talk will first review the evolution of intra-data center interconnects over the past decade, then outline future opportunities of optics beyond networking. We will discuss optical and electrical devices, advanced modulation technologies and packaging innovations that deliver better performance and energy efficiency for applications including data center networking and machine learning. Requirements in 400G/800G short reach and long reach optical transceivers, coherent transceiver for intra-datacenter, fiber to machine, and die to die optical interconnects will be discussed.

Optical routing typically makes use of nodes located at various places around the optical network. However, many locations can be vulnerable to failure due to the potential for power to be interrupted at optical networks, leading to performance degradation, because the network routing node itself typically requires an electrical DC bias voltage and a control signal. In addition, another key challenge is monitoring the state of the node, especially due to bias and temperature drifts that are common in typical Mach–Zehnder interferometers (MZIs) or nonlinear waveguides such as periodically-poled-lithium-niobate (PPLN) waveguides. One approach could be to use bidirectional transmission of multiple laser sources over an optical link. Subsequently, (i) arrays of photodiodes that are driven from remote laser sources are used to enable biasing and controlling; (ii) pilot tones are transmitted and their ratios after backpropagation are observed in the transmitter side to monitor the state of operation and adjust the optical powers accordingly. This paper highlights certain architectures for remotely biasing, controlling, and monitoring a network node that lacks local power, which might enable flexible optical networking. These architectures include: (i) an MZI-based optical switch with optically delivered control and data signals as well as a remotely controlled and monitored optical correlator based on either (ii) delay line interferometer (DLI) or (iii) nonlinear wave-mixing in a PPLN waveguide for a QPSK data.

We present an algorithmic approach that offers an efficient way of multiple lightpaths reconfiguration, either for increased traffic requests, or lightpath restoration. It permits the building of a feasible optical network design considering the available spectrum, traffic demand characteristics, network topology, equipment configurations, and engineering constraints. We show the employment of methods for calculating and provisioning multiple lightpaths. Our approach is flexible enough to accommodate optical network topologies of different types and sizes. The result is a lightpath configuration that is optimized for spectrum utilization and GSNR degradation.

We review the progress of BDFA development for O-band amplification. Currently, BDFAs can provide up to 35 dB small signal gain, less than 5.5 dB noise figure, and up to 29 dBm output power over 1270-1360 nm. We discuss amplifier design issues including pump wavelength and bandwidth allocation, as well as components performance and availability. Recent transmission experiments including LAN-WDM and CWDM modules reach extension over the spooled fiber and installed cables will be presented. Future milestones in BDF/BDFA development would also be suggested. Since with the implementation of BDFAs the transmission over O-band would no longer be power budget limited, we will briefly discuss the options of chromatic dispersion compensation over O-band.

A single input to multiple output optical concentrator is presented that can split a millimeter-scale input area into multiple sections and concentrate each section into a separate output. Ray trace simulations are used to evaluate the incidence angle tolerance for linear taper designs with a 3mm length and geometric concentrations up to 64x. We present simulations for a 1x7 taper design and the first fabrication results using fused silica as the cladding and Norland Optical Adhesive with n=1.51 as the core material. The optical throughput measurements indicate excellent splitting uniformity with a standard deviation of 0.26dB.

In this paper, an overview the coherent transceiver modules such as the 400ZR and 400ZR+ is presented including interoperability test results. Additionally, technologies for 800G modules for the DCI (800ZR) and 2-10 km campus links (800LR), and a comparison of coherent vs. IMDD formats for 800G and higher rate transceivers are discussed.

Commercial deployment of optical interconnects has benefited significantly from the advances in silicon photonics and on-chip integration of various components, active and otherwise. As the technology continues to mature and evolve, a few critical components and capabilities require close attention to enable successful adoption of co-packaged photonics. In this talk, I will outline system-level requirements for packaging, assembly, fiber connectors and laser requirements for advanced AI.