Cisco QSFP-DD Pluggable Open Line System (QDD OLS) Data Sheet

The QSFP-DD OLS is a pluggable open line system solution that can be directly hosted on a Cisco router.

Product overview

The Cisco^® QSFP-DD Open Line System (QSFP-DD OLS) is a pluggable optical amplifier module that, together with the channel breakout options (described later), provides a simple yet powerful open line system solution in a QSFP-DD pluggable form factor (also compatible with QSFP28) that can be directly hosted on a Cisco router.

Cisco offers a comprehensive range of pluggable optical modules in the Cisco pluggables portfolio. The wide variety of modules gives customers flexible and cost-effective options for all types of interfaces. Thanks to the miniaturization of the technology with a 7-nm manufacturing procedure and innovation in silicon photonic technology, it was possible to squeeze a 400G-capable Digital Coherent WDM interface within a QSFP-DD form factor.

This innovation first lead to the release of Cisco QSFP-DD ZR and QSFP-DD ZR+ interfaces. While these were industry-leading Coherent DWDM interfaces at the time of their launch, the transmit power of –10dBm left customers needing additional amplification at the sources to launch at a healthy power into the transmission fiber. The distances were thus restricted to 40 km, and a limited set of add/drop configurations compliant with that low transmit power could be used in the line system configuration.

In parallel, Cisco’s Routed Optical Networking (RON) strategy was born, which envisioned a router to router architecture. Routed Optical Networking, part of the Converged SDN Transport solution, is an architecture that delivers improved operational efficiencies and simplicity. The solution works by merging IP and private line services onto a single layer where all the switching is done at Layer 3. Routers are connected with standardized 400G ZR/ZR+ coherent pluggable optics. The Cisco vision for this new solution is to leverage the fundamental lifecycle changes happening in routers and optics and utilize those technologies in a different architecture. These technological advancements result in massive scalability in the Cisco 8000, NCS 5000, and NCS 500 routers, a smaller footprint and higher performances 400G ZR/ZR+ coherent optics, and simpler DWDM line systems, telemetry software, and automation, all leading to a new network paradigm. The QSFP-DD ZR, ZR+ and Bright ZR+ interfaces are the foundation of the Cisco Routed Optical Networking solution.

The low transmit power of the QSFP-DD ZR, ZR+ required customers to deploy an optical amplifier at the end points of a link/fiber span connecting the routers in the Cisco RON solution, to achieve a longer than 40km reach.

Cisco designed an ingenious solution to collapse the optical line system functionalities into a pluggable form factor. The QSFP-DD open line system (QSFP-DD OLS) can be directly deployed in a router alongside other QSFP-DD optics, using any available QSFP-DD port. This “pluggable open line system” perfectly integrates into the Cisco Routed Optical Networking architecture by hosting line system abilities directly on a router.

The 400G Bright QSFP-DD optics is able to launch at a much higher (+1dBm) transmit power. Even with this new version of the 400G ZR+ the QSFP-DD OLS still provides value as it further extends the reach of the 400G Bright QSFP-DD optics beyond the 80 to 120 km limit and, more importantly, it enables the support of a multichannel line system directly in the router. The ability to extend the reach and capacity of a single fiber span in a Cisco Routed Optical Networking architecture is the standout value of this QSFP-DD OLS solution, immaterial of which interface is being used.

The QSFP-DD pluggable open line system

1x8 breakout cable (left), CS-LC cable (right)

Features and benefits

The QSFP-DD OLS itself is a pluggable module that integrates two variable-gain amplifiers (a pre-amplifier and a booster amplifier) to amplify both the up and down fiber streams. Various channel breakout options are available to combine or separate each channel from a coherent DWDM optical source. The TX-EDFA acting as a Booster amplifier recovers the loss of the optical Multiplexer unit, and it provides an optical power boost before the link. The RX-EDFA acting as Preamp recovers the link loss, bringing the optical signal to a power level optimized for the receivers after the Demultiplexer unit.

The QSFP-DD OLS can extend the reach of a 400G QSFP-DD ZR/ZR+ link (from 40 to 130 km or longer, depending on fiber characteristics), the channel count, and the line rate of the wavelength.

To integrate a pair of ingress and egress ports on the QSFP-DD OLS pluggable faceplate, industry-standard CS-UPC connectors are used. The QSFP-DD-OLS has two bidirectional optical ports: the COM-RX/TX that shall be connected to the Multiplexer / Demultiplexer units, and the LINE-TX/RX that shall be connected to the fiber link. The optical connectors are 2x CS-UPC, each providing the characteristics and simplicity of the duplex LC connector into a smaller footprint, hence allowing four physical ports to fit on the faceplate of the QSFP-DD form factor. Since the other optical units (Coherent Interfaces modules, DWDM Add/Drop multiplexers, and fiber patch panels) normally use LC connectors, a hybrid adaptation patch cord with a CS dual connector on one side and 2x LC connector on the other side is available to interconnect the QSFP-DD-OLS module with other optical equipment.

Optical safety is enabled by default to:

●      Switch off each optical amplification section independently in case Optical LOS is detected at its input

●      Set the TX-EDFA in Automatic Power Reduction (APR) at 8dBm in case a LOS is cleared at the COM-RX port, but LOS is still present at LINE-RX (this prevents the launch of high optical power on an open line)

An N-channel WDM line system can be built using the QSFP-DD OLS and its associated components:

A single channel system

It requires no special components to add and drop. A 5 meter long CS-LC cable (ONS-CAB-CS-LC-5) is available to interconnect the LC ports of the QSFP-DD coherent source or the span fibers with the CS ports of the QSFP-DD OLS. Two of these cables are needed for each end point of a single channel system. All the gain of the amplifiers is available for the single channel to be transported in this case.

A 4-channel system

To achieve a 4-channel transmission, an FLD-4 (fixed 4 channel OADM) can be used. This passive optical Add/Drop unit is able to multiplex/demultiplex 4 channels over the 100GHz ITU grid. There are 10 different Cisco FLD-4s (each managing 4 adjacent channels) available, each identified by the xy.x numbers and covering the whole C-band. Only 6 of the 10 FLD-4 PIDs are compatible with the QSFP-DD-OLS optical operating bandwidth as listed in Table 1. A 5 meter long CS-LC cable (ONS-CAB-CS-LC-5) is available to interconnect the LC ports of the A/D or the span fibers with the CS ports of the QSFP-DD OLS.

An 8-channel system

To achieve an 8-channel transmission, an 8 channels breakout cable can be used. This breakout cable (ONS-BRK-CS-8LC) is a dual fanout 1x8 cable with an embedded passive splitter and coupler. The cable has one dual CS/UPC connector on the common port that can be directly connected to the COM port of the QSFP-DD-OLS and 8 dual LC/UPC (labelled CHi-RX/TX) that can be connected to a Coherent Optical Interface modules port. The cable is grid-less so any port can support any optical frequency without any constraint of frequency or channels spacing.

A 16-channel system

To achieve a 16-channel transmission, a 16 channels breakout cable can be used. This breakout cable (ONS-BRK-CS-16LC) is a dual fanout 1x16 cable with an embedded passive splitter and coupler. The cable has one dual CS/UPC connector on the common port that can be directly connected to the COM port of the QSFP-DD-OLS and 16 dual LC/UPC (labelled CHi-RX/TX) that can be connected to a Coherent Optical Interface modules port. The cable is grid-less so any port can support any optical frequency without any constraint of frequency or channels spacing.

A 32-channel system

To achieve a 32-channel transmission, a 64-channel mux/dmx can be used (of which 32 channels are used). The NCS1K-MD-64-C is a passive optical Add/Drop unit able to multiplex/demultiplex up to 64 channels over the 75GHz grid. The operating bandwidth of the QSFP-DD-OLS allows a subset of the MD-64 channels to be used: form port CH-19 (194.75 THz) to port CH-50 (192.425 THz).

An 8-channel point-to-point configuration with the QSFP-DD OLS

Product specifications

A simple on-paper calculation considering the QSFP-DD OLS gain, power in/out of the fiber, the N-channel Add/Drop device, and the sensitivity of the QSFP-DD optical source can yield a link design. Cisco is readily available to support customers for links design.

The following table lists out the Add/Drop options to achieve an N-channel system.

Table 1.        Add/Drop options for QSFP-DD line system solution

The following table lists out the specification of various components that form the QSFP-DD Open Line system solution.

Table 2.        Specifications of the QSFP-DD OLS components

Platform support

The Cisco QSFP-DD OLS can be directly configured and managed by the IOS^® XR SW on board Cisco routers. Below are the router platforms/products and software release that are currently supported.

Table 3.        Supported platforms

Ordering information

Table 4.        List of orderable PIDs associated with the QSFP-DD OLS solution

Table 5.        List of associated 400G coherent optical sources

Warranty

Product warranty terms and other information applicable to Cisco products are available at www.cisco.com/go/warranty.

Product sustainability

Information about Cisco’s Environmental, Social, and Governance (ESG) initiatives and performance is provided in Cisco’s CSR and sustainability reporting.

Table 6.        Cisco environmental sustainability information

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