Electronic Design
Optical Breakthroughs Put 40/100 Gigabit On The Fast Track

Optical Breakthroughs Put 40/100 Gigabit On The Fast Track

The 40- and 100-Gbit/s fiber network’s imminent larger-scale rollout was clearly evident at the Optical Fiber Communication Conference and Exposition (OFC) 2010 in San Diego in March. The show teemed with product introductions from a range of companies.

PROXIMION

Proximion Fiber Systems AB, which specializes in dispersion compensation modules (DCMs) based on Fiber Bragg Grating (FBG), added two new versions of its tunable DCM (TDCM) (Fig. 1). Employing the company’s proprietary FBG technology, the modules increase flexibility while offering wider continuous tunability ranges to meet growing network needs.

The first new TDCM was prompted by customer demand for increased tunability, leading to a ±1400-ps/nm tunable range at a bandwidth operation of 45 GHz. The second new module version, also operating at 45 GHz, enables full flexibility while reaching truly “colorless” tuning over ±1200 ps/nm. With their low-power 1.5-W consumption, low loss, and wide bandwidth, these TDCMs should easily support the high-performance dispersion compensation required for a growing number of 10G and 40G applications.

NETLOGIC MICROSYSTEMS

An extensive series of high-performance networking and communications physical-layer (PHY) products, developed by NetLogic Microsystems, specifically targets 10/40/100-Gigabit Ethernet and 8.5-Gigabit Fibre Channel. The new highly integrated single-, dual-, and quad-port PHY devices, which offer ultra-low jitter, low-latency, and low-power capabilities, support multiple protocols and multiple media types. These include single-mode fiber (SMF), multimode fiber (MMF), and direct-attach copper and target high-density data center and enterprise applications. They are all manufactured with advanced process technologies, such as TSMC’s 40-nm node.

The NLP10142C 100GE and NLP10142X 40GE PHY, respectively, feature an innovative architecture and advanced circuit technologies to significantly boost jitter performance and lower power consumption. The NLP10142C 100GE PHY supports 100-Gbit/s transmissions over at least 40 km on SMF cabling, at least 100 m on OM3 MMF, or at least 10 m over a copper cable assembly.

At OFC, the company successfully demonstrated 100GE based on an MLD-to-CPPI (multi-lane distribution to communications port programming interface) application with a 100G CXP module. It also demonstrated 40GE based on a MLD-to-XLPPI (40-Gigabit parallel physical interface) application with a 40G QSFP+ module.

These devices exceed all electrical parameters of the nPPI interface as defined in P802.3ba Annex 86A, and they fully comply with the CR4/CR10 PMDs as defined in P802.3ba Clause 85. (802.3ba is the IEEE’s designation for the 40- and 100-Gbit/s Ethernet standards.) The NLP10142C and NLP10142X PHY come in lead-free packaging, allowing customers to develop environmentally friendly system solutions that comply with certain green-initiative regulations.

NetLogic Microsystems also demonstrated 10GBASE-KR for backplane applications using the AEL3020 PHY device, which supports up to 40 inches of FR4 backplane traces with two connectors. The AEL3020 PHY integrates the company’s established electronic-dispersion-compensation (EDC) technology and complies with IEEE 802.3aq LRM and 802.3ap KR standards.

Link diagnostic capabilities implemented in the device include voltage-time offsetting, bit error rate (BER) calculators, and traffic monitors. When complemented with highly programmable Ethernet frame, pseudo-random binary sequence (PRBS), and custom test-pattern generators and checkers, they can provide highly granular data on the health of a high-speed serial link in a dense and crosstalk-dominated backplane environment. Integrating external board passives and a highly simplified power-supply distribution circuit allows for high-density layouts in area-constrained designs.

Another announcement from NetLogic—the NLP1220 dual-channel, 8.5-Gbit/s Fibre Channel device—claims best-in-class power consumption and latency for customers developing next-generation data-center switches and storage host bus adapters (HBAs). The repeater device supports 2/4/8G auto-negotiation capability. It integrates the receiver and transmitter serializer-deserializer (SERDES) functions on one with on-chip clock drivers, multiple loop-back features, and PBRS generation and verification for both the line side and system side. A low-power equalization engine doubles the reach of Fibre Channel signals on printed-circuit board (PCB) traces and cables, supporting up to 15 m on 24/26 AWG cables and up to 10 m on 30 AWG cables.

LUXTERA

Leveraging its expertise in silicon CMOS photonics, Luxtera jumped into the 40G Ethernet fray with its OptoPHY solution. As 10G Ethernet connections migrate to server connectivity, 40G Ethernet is emerging as a preferred solution for switch interconnect, delivering the bandwidth necessary for aggregation of multiple servers. To expedite the wide deployment of 40G Ethernet, a low-cost optical interconnect is required.

According to Luxtera, OptoPHY (Fig. 2) is the first CMOS photonics-based single-chip transceiver for on-board deployment. The device overcomes cost barriers that often malign optics. It also offers lower power consumption and longer reach than legacy copper and VCSEL-based (vertical cavity surface-emitting laser) multimode fiber transceivers.

OptoPHY features a smaller form-factor than traditional MSA modules and suits switch-interconnect and network-interface-controller (NIC) applications on servers. The solution complements standard multi-source agreement (MSA) transceivers, such as Luxtera’s Blazar, a 40G quad small form-factor pluggable (QSFP) active optical cable. The company has worked with technology partners Tektronix and NetLogic Microsystems to apply its optical technology.

Another target area for the transceiver involves server-to-switch interconnects in data centers. Data centers continue to strive for energy efficiency to reduce operation costs and comply with emerging “green” laws and regulations. As such, OptoPHY’s board-mountable, optical transceivers extend to 4000 m, consuming under 200 mW per 10G and offering fiber-optic electromagnetic interference (EMI) immunity.

Luxtera’s Silicon CMOS Photonics technology, interoperating with NetLogic’s low-power 10GbE SERDES technology, offers a solution for low-power, low-latency links needed in data-center connectivity. To address the immediate need for 40-Gbit/s connectivity, next-generation 40-Gbit/s links based on Luxtera’s QSFP+ modules and NetLogic’s 40G PHY devices are currently in the works.

NEOPHOTONICS

A new line of 10G passive optical network (PON) transceivers from NeoPhotonics made its mark at OFC. The transceivers, compliant with the ITU-T G987.2 and IEEE 802.2av networking standards, will find homes in “fiber to the premise” (FTTP) networks. Along with the company’s gigabit PON (GPON) and gigabit Ethernet PON (GEPON) modules, the novel 10G transceivers target optical line terminals (OLTs) and optical networking units (ONUs), which are typically deployed in central offices (CO) and at customer premises (CPE), respectively.

The ITU-T G987.2-compatible transceivers support data rates of 10G in the downstream direction and 2.5G burst-mode transmission in the upstream direction, covering nominal link budgets of 29 and 31 dB. The IEEE 802.3av-compatible transceivers support 10G in the downstream direction and 1G burst-mode transmission in the upstream direction, covering link budgets of up to 30.5 dB.

The OLT transceivers come in the XFP form factor, while the ONU transceivers are available in the space-saving and power-saving SFP+ form factor. Monitoring features allow for early fault location and reduce down time in system operation.

NeoPhotonics also announced the initial availability of its integrated coherent receiver (ICR) for 100- and 40-Gbit/s transmission systems. The ICR is an integrated intradyne receiver based on the company’s Photonic Integrated Circuits (PIC) technology.

The device’s advanced demodulation analyzes the state-of-polarization and optical phase of a phase-modulated signal relative to an externally supplied optical reference. This makes it possible to recover the phase-polarization constellation of 100-Gbit/s dual-polarization differential quadrature phase-shift-keyed (DP-DQPSK) format signals.

In addition, the ICR incorporates four sets of high-sensitivity balanced photodiodes with four differential linear amplifiers to provide four output channels at 32-Gbaud data rates. A second version performs the same function for 40-Gbit/s applications.

The ICR uses NeoPhotonics’ hybrid PIC technology to combine an integrated dual 90° hybrid coherent mixer with four balanced photodiodes and the requisite linear amplifiers in a single compact package. The company is an active contributor in the Optical Internetworking Forum (OIF) 100G project, particularly in regards to the integrated photonics receiver.

NeoPhotonics’ 90° hybrid coherent mixers and DQPSK demodulators are based on PIC technologies. The mixer provides the demodulation function of the ICR, requires no electrical power, operates across the C or L band and can be used with external photo-receivers. The DQPSK demodulator consists of two delay line interferometers (DLIs) and delivers in-phase and quadrature analysis of a phase-encoded signal.

Luxtera Inc.

NetLogic Microsystems

NeoPhotonics Corp.

Proximion Fiber Systems AB

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