Cisco QDD-400G-ZRP-S QSFP-DD Transceiver Module

Product Overview: Cisco QDD-400G-LR4-S — High-Density 400G QSFP-DD Transceiver

The Cisco QDD-400G-LR4-S is a high-performance 400G QSFP-DD transceiver engineered for long-reach single-mode fiber links. Optimized for data centers and core routing environments, this module delivers reliable 400 Gbps throughput over duplex LC connections to spans up to 10 kilometres. Designed by Cisco to meet stringent carrier and enterprise grade requirements, the QDD-400G-LR4-S supports 400GBASE-LR4 signalling across four distinct wavelengths for robust, low-latency transport.

Key Features and Capabilities

• Form factor: QSFP-DD (Quad Small Form Factor Pluggable Double Density) for ultra-dense port aggregation.
• Aggregate data rate: 400 Gbps, supporting next-generation backbone and spine architectures.
• Fiber type: Single-mode fiber (SMF) using duplex LC connectors for standardised interoperability.
• Link reach: Up to 10 km over SMF, ideal for campus interconnects and metro links.
• Wavelengths: Four lanes at approximately 1270 nm, 1290 nm, 1310 nm, and 1330 nm (LR4 DWDM-style spacing).
• Protocol support: Compatible with Gigabit Ethernet and 400GBASE-LR4 specifications for broad equipment compatibility.
• Vendor: Cisco — engineered to Cisco quality and tested for compatibility with Cisco switching and routing platforms.

Technical Specifications

General

• Manufacturer: Cisco
• Part number / SKU: QDD-400G-LR4-S
• Product family: Optical transceiver modules — 400 Gbps class
• Form factor: QSFP-DD (double density QSFP)

Optical & Electrical

• Data rate: 400 Gbps aggregate (4 × 100 G lanes)
• Fiber: Single-mode fiber (SMF)
• Connector: Duplex LC
• Wavelengths: 1270 nm / 1290 nm / 1310 nm / 1330 nm
• Maximum reach: 10 kilometres (over standard SMF, channel dependent)

Protocol & Interoperability

• Standards compliance: 400GBASE-LR4 and related IEEE/ITU specifications
• Data link protocols: Gigabit Ethernet and higher-rate Ethernet fabrics
• Compatibility: Engineered for seamless operation with Cisco switches and routers that accept QSFP-DD optics; also interoperable with other standards-compliant 400G ports where vendor cross-compatibility exists.

Why Choose QDD-400G-LR4-S?

This transceiver is ideal when you need a combination of density, distance and stability. The QSFP-DD form factor gives you double the lane density compared with standard QSFP modules, reducing port real-estate while delivering 400 Gbps per port. The LR4 variant is purpose-built for longer single-mode spans, making it a practical choice for connecting data halls, edges, and metro aggregation nodes without sacrificing throughput or reliability.

Performance Advantages

• High throughput per port reduces the number of physical links required between core and aggregation layers.
• Deterministic wavelength lanes reduce cross-talk and enhance signal integrity over longer SMF runs.
• Energy-efficient design improves power-per-bit metrics in large-scale deployments.

Operational Benefits

• Easy hot-plug installation in QSFP-DD-capable slots, simplifying upgrades and field replacements.
• Vendor-backed reliability and testing from Cisco for predictable network behavior.
• Standard duplex LC interface for straightforward cabling and lower operational complexity.

Typical Use Cases

Data Center Spine and Core

Ideal for high-capacity spine links where aggregation of multiple 400G ports reduces the total switch count and cabling complexity.

Inter-Data-Hall Connectivity

Provides cost-effective 10 km reach for linking adjacent data halls or campus buildings over single-mode fiber.

Metro and Service Provider Edge

Useful for carrier aggregation and metro ring segments where 400G capacity and LR4 reach are required.

Installation, Compatibility & Best Practices

Pre-Installation Checklist

• Confirm the target switch/router has QSFP-DD slots and supports 400GBASE-LR4 optics.
• Verify single-mode duplex LC patching and that the fiber run is certified for 10 km spans.
• Ensure firmware and platform transceiver compatibility lists include Cisco QDD-400G-LR4-S to avoid link negotiation issues.

Deployment Tips

• Use high-quality LC connectors and pre-tested fiber paths to minimise insertion loss.
• Label both ends of the duplex LC pair and document lane assignment for faster troubleshooting.
• Monitor transceiver diagnostics (where supported) for temperature, bias, and optical power metrics to detect degradations early.

Compatibility & Interchangeability

While built by Cisco and validated on Cisco platforms, the QDD-400G-LR4-S adheres to industry standards for optical signalling. Where interoperability is critical, check the network equipment vendor’s compatibility matrix and test links in a lab environment before full production rollout. For mixed-vendor networks, review link capabilities and enable any necessary platform settings for multi-vendor optics.

Supported Interfaces and Protocols

• Interface: Duplex LC optical connector
• Link protocol: 400GBASE-LR4 with backward compatibility for Ethernet-based fabrics
• Management: Digital diagnostics monitoring (DDM) support subject to host platform capabilities

Quick Reference — At-a-Glance

• Model: Cisco QDD-400G-LR4-S
• Type: 400G QSFP-DD transceiver
• Fiber: Single-mode (SMF), Duplex LC
• Rate: 400 Gbps
• Wavelengths: 1270 / 1290 / 1310 / 1330 nm
• Max distance: 10 km
• SKU: QDD-400G-LR4-S

Frequently Asked Questions

Is the QDD-400G-LR4-S hot-swappable?

Yes — when used in platforms that support QSFP-DD optics the module can be hot-plugged, but follow standard operational procedures to avoid transient link issues.

Can this module work with multimode fiber?

No — this LR4 variant is engineered for single-mode fiber. Using multimode fiber will not meet the specified 10 km reach and is not recommended.

What should I check if a link does not come up?

Confirm physical cabling, platform firmware compatibility, transceiver seat (fully inserted), and that the port is configured for 400G operation. Reviewing DDM telemetry and platform logs often points to the root cause.

Purchase Considerations and Lifecycle

When procuring the QDD-400G-LR4-S, account for lifecycle planning: ensure spare modules are stocked, plan firmware and platform upgrades to maintain interoperability, and factor eventual migration paths (e.g., 800G or alternate optics) into capacity forecasts. Cisco’s part number QDD-400G-LR4-S simplifies ordering and warranty tracking.

Overview — Cisco QDD-400G-ZRP-S (QSFP-DD coherent DCO, 400G-ZR+)

The Cisco QDD-400G-ZRP-S is a QSFP-DD form-factor coherent digital coherent optics (DCO) transceiver engineered for high-capacity long-reach DWDM transport. Designed to support 100G–400G programmable line rates using advanced modulation (DP-QPSK, DP-8QAM, DP-16QAM) and integrated coherent DSP, this module provides a compact, pluggable option for service providers, cloud operators, and large enterprises that require metro to regional reach with low rack-space and power overhead.

Key capabilities at a glance

• Form factor: QSFP-DD (double-density QSFP) compatible with OIF MSA interoperable ports.
• Technology: Coherent DCO with integrated tunable laser and coherent DSP ASIC.
• Nominal speed: Programmable — supports 100G, 200G, 300G, 400G line rates depending on modulation and baud configuration.
• Standardized reach: Targets the ZR / ZR+ class for single-span DWDM (common deployments up to ~80–120 km, depending on amplification and channel plan).
• Connector type: LC duplex for single-mode fiber (SMF) DWDM links.
• Wavelength tuning: C-band tunable across DWDM ITU channels (typical range ~1528.77 nm – 1567.13 nm).

Technical deep dive — optics, modulation and performance

Coherent optics and DSP

Unlike direct-detect pluggable modules, the QDD-400G-ZRP-S integrates a coherent receiver and transmitter together with a high-performance DSP. This DSP performs carrier recovery, polarization demultiplexing, chromatic dispersion compensation, and advanced forward error correction (FEC). The result is high spectral efficiency and robust performance over dispersion-laden DWDM links without the need for inline dispersion compensation modules in most metro/regional use cases.

Supported modulation formats and baud options

• DP-QPSK — commonly used for robust 100G/200G links at lower OSNR requirements.
• DP-8QAM — enables intermediate tradeoffs between reach and spectral efficiency (typical for 300G).
• DP-16QAM — used to hit the 400G line-rate where link OSNR and fiber plant permit.
• Baud rates (illustrative): modules often support ~32G–64G symbol rates (vendor variants vary), with DSP selecting optimum baud and framing for a target throughput and reach.

Because the transceiver is programmable, network operators can tune modulation/baud to match link conditions, trading capacity for reach when necessary (for example, falling back from 400G/16QAM to 200G/QPSK to extend reach or improve margin).

Typical reach & channel plan

The QDD-400G-ZRP-S is often described as a ZR+ (ZR PLUS) grade coherent module — intended for DWDM point-to-point links in metro and regional networks. Typical vendor documentation and field deployments target reach up to ~80–120 km over standard single-mode fiber when used with appropriate amplification (EDFA) and channel planning. Realized reach depends on:

• Fiber span loss and amplifier chain (EDFA placement and tilt).
• Channel spacing (flex-grid / fixed grid) and neighboring channel power.
• Target modulation format and required OSNR for chosen QAM order.
• Use of ROADMs, optical add/drop multiplexers, or additional inline components.

Hardware compatibility & platform considerations

Supported platforms & port mapping

Cisco documents and platform release notes list specific QSFP-DD DCO compatibility (supported ports and operational constraints). For example, certain router and switch families support QDD-400G-ZR-S models on specific 400G ports only, and host systems may impose cooling or redundant power requirements when operating coherent DCO modules at scale. Always check the target platform’s transceiver support matrix before procurement and installation.

Thermal and power notes

Coherent DCO pluggables typically consume more power and generate more heat than direct-detect optics. Platform vendors recommend:

• Using qualified power supplies (higher wattage PSUs where required).
• Ensuring adequate chassis airflow (port-side intake fans, proper fan trays).
• Following per-port and per-chassis thermal limits — many installation guides highlight reduced supported ambient temperature when DCO modules are inserted densely.

Deployment scenarios and use cases

Cloud and data center interconnect (DCI)

When operators need a compact, low-OPEX method to interconnect colocation sites, campuses, or adjacent data centers, QSFP-DD coherent modules are compelling: they enable 400G wavelengths in a pluggable form factor so that router or switch ports (with QSFP-DD cages) can transmit native high-rate DWDM channels without separate transponder shelves. This reduces capital expense and rack space while simplifying operations.

Metro aggregation and regional rings

For metro aggregation rings (e.g., connecting multiple POPs across a city or region) the QDD-400G-ZRP-S provides:

• Flexible capacity — dial up/down line rate as traffic patterns change.
• Interoperability with DWDM ROADM systems when used as line-side coherent wavelengths (verify vendor compatibility for ROADMs and filter profiles).
• Lower per-bit cost versus discrete transponder + mux/demux appliances in many topologies.

Service provider backbone & wholesale optical services

Carriers delivering wavelength, Ethernet private line, or hosted services can use 400G DCO pluggables to inventory flexible wavelengths delivered directly from service router/switch ports. This simplifies operations and provides faster service turn-up cycles by eliminating separate transponder provisioning.

Integration & provisioning best practices

Link design checklist

• Confirm module support on both ends — verify platform model, OS release, and transceiver firmware compatibility.
• Calculate link budget: sum span loss, connector loss, and margin; account for ROADMs and filters.
• Decide on modulation strategy — pick initial baud/QAM for the required reach and capacity.
• Define channel plan (ITU grid channel number or frequency) and engage DWDM ops to allocate the C-band slot.
• Test in lab if possible — sweep fiber and measure OTDR/OSNR to validate expected performance.

Operational tuning & monitoring

The module supports digital optical monitoring (DOM) telemetry for key parameters (laser bias, temperature, optical power, and alarm states). Coherent modules typically also expose additional telemetry via the host OS (DSP alarms, OSNR estimate, and modulation state). Integrate these sensor readings into your NMS for proactive fault detection and capacity planning.

Compatibility, interchangeability and vendor equivalence

MSA and ecosystem interoperability

The QSFP-DD DCO family follows industry MSA and OIF guidance for coherent pluggables, enabling cross-vendor compatibility between modules that adhere to the same mechanical and optical standards. That said, platform acceptance and software validation can vary between OEMs; "3rd-party compatible" modules are widely available and tested to be interoperable with Cisco platforms but always validate support documentation and warranty/return policies prior to purchase.

When to buy OEM vs compatible modules

• OEM (Cisco) genuine modules: guaranteed compatibility, vendor support, and firmware/feature parity. Suitable when warranty/contractual compliance matters.
• Third-party compatible modules: often cost-effective, may be 100% functionally compatible, and are commonly provided with lifetime or multi-year warranties from reputable resellers. Important to confirm interoperability and return policies.

Procurement & lifecycle considerations

Stocking and spares strategy

Because coherent DCO modules are a high-value line item, organizations should adopt a careful spares policy. Factors to consider:

• Lead times — some models can have multi-week lead times; plan for business continuity needs.
• Firmware baseline — coordinate module firmware revisions with platform OS versions to avoid incompatibilities after field insertion.
• Inventory rotation — store spares in controlled temperature to avoid degradation; log serials for warranty tracking.

End-of-life and upgrade path

Coherent pluggables are part of an evolving ecosystem: newer DSPs and photonics continue to raise spectral efficiency and reduce power per bit. When planning upgrades, consider:

• Whether your platform can accept newer QSFP-DD DCO variants without hardware changes.
• Backward compatibility needs — whether legacy remote sites require stepwise migration (e.g., fallback to 200G modes).
• Lifecycle of optical line equipment (ROADMs, EDFAs) — ensure the optical layer supports future modulation and flex-grid features if you plan to increase wavelength density.

Security, management & automation

Monitoring and telemetry

Modern coherent modules provide rich telemetry (power, temperature, bias currents, OSNR estimates, DSP alarms). Expose these through the host device’s management APIs (CLI, SNMP, streaming telemetry) and correlate with transport layer counters to automate fault isolation and thresholding. This enables predictive maintenance — for example, escalating fiber cleaning or amplifier tilt adjustments before service impact occurs.

Firmware & field upgrades

Modules may receive firmware updates from the vendor to improve performance or fix issues. Coordinate firmware updates across your fleet and validate on non-production hardware first. Maintain a strict rollback plan and keep serial-linked records of firmware versions for support cases.

Comparisons — QDD-400G-ZRP-S vs other 400G options

Pluggable DCO vs standalone transponders

Direct-detect 400G optics (SR/DR) vs coherent ZR+

Direct-detect 400G optics (SR, DR) are optimized for short reach (up to a few hundred meters to a few kilometers), while coherent ZR+ modules like the QDD-400G-ZRP-S are designed for DWDM, metro, and regional spans with significantly longer reach and optical amplification. Choose direct-detect when you need low-latency, short-reach interconnects; choose coherent pluggables when you require long-haul or high-OSNR-sensitive transport.

Troubleshooting & field maintenance

Common issues and remedies

• Link won't establish: verify channel allocation, ensure both ends are on the same ITU channel and that fiber polarity is correct.
• High pre-FEC BER or margins low: check OSNR, amplifier tilt, and fiber attenuation; consider lowering modulation order or moving to a lower baud configuration.
• Module not recognized by host: confirm platform transceiver whitelist, firmware compatibility, and that the module serial/EEPROM is intact. Reboot or reseat if safe to do so.
• Temperature or power alarms: check chassis fans, PSU health, and ambient temperature limits. Move modules to better-cooled slots if required.