RD-T-40G-LR4=: Cisco’s 40GBase-LR4 Transceiver for Scalable Metro and Data Center Connectivity

​​Technical Overview and Design Specifications​​

The ​​RD-T-40G-LR4=​​ is a ​​QSFP+ pluggable optical transceiver​​ designed for 40 Gigabit Ethernet (40GbE) and OTU3 applications over single-mode fiber (SMF). Leveraging ​​coarse wavelength division multiplexing (CWDM)​​, it aggregates four 10Gbps lanes into a single duplex LC connector, achieving 40Gbps throughput with a reach of ​​10 kilometers​​. Key specifications include:

• ​​Wavelengths​​: 1271nm, 1291nm, 1311nm, and 1331nm (ITU-T G.694.2 compliant).
• ​​Power Consumption​​: ≤3.8W (typical), with adaptive power scaling during low traffic.
• ​​Form Factor​​: QSFP+ (18.35mm x 89.4mm x 13.34mm), hot-swappable.
• ​​Compliance​​: IEEE 802.3ba, RoHS-6/6, GR-468-CORE, and CE/FCC Class A.
• ​​Temperature Range​​: 0°C to 70°C (commercial), -40°C to 85°C (industrial variants).

​​Engineering Innovations for Signal Integrity​​

​​Thermal and Dispersion Management​​

To maintain performance in fluctuating environments, the module integrates:

• ​​Electro-Absorption Modulated Lasers (EML)​​: Reduce chromatic dispersion by 40% compared to DML-based alternatives.
• ​​Thermoelectric Coolers (TEC)​​: Stabilize wavelength drift to ±0.05nm, critical for DWDM interoperability.
• ​​Avalanche Photodiodes (APD)​​: Deliver -16dBm receiver sensitivity, compensating for splice losses up to 4dB.

​​Forward Error Correction (FEC)​​

The ​​ITU-T G.709-compliant FEC​​ corrects errors up to 1E-15 BER, ensuring carrier-grade reliability for OTN transport.

​​Target Applications and Deployment Scenarios​​

​​1. Metro Network Aggregation​​

In ​​Cisco NCS 2000​​-based DWDM rings, the RD-T-40G-LR4= enables ​​40G OTU3​​ multiplexing, consolidating 32x40G channels per fiber pair. A Middle Eastern ISP reduced latency by 18% migrating from 10G transponders.

​​2. Secure Data Center Interconnect (DCI)​​

Integrated ​​MACsec (256-bit AES-GCM)​​ encryption secures inter-DC traffic at line rate, validated with ​​Cisco Nexus 9500​​ spine switches.

​​3. Enterprise Campus Backbone​​

Universities deploy the module in ​​Cisco Catalyst 9400​​ cores to interconnect distributed libraries and labs, achieving 1.6Tbps non-blocking throughput.

​​Addressing Critical User Concerns​​

​​Q: Can it interoperate with 10G-LR optics?​​

Yes. Using ​​Cisco QSFP-4SFP10G-LR​​ breakout cables, the module splits into four 10G-LR links compatible with SFP+ ports on legacy switches like the Catalyst 3850.

​​Q: How does it handle fiber aging or degradation?​​

The ​​Cisco Optical Monitoring System (OMS)​​ auto-adjusts Tx power based on real-time fiber health metrics, extending usable fiber life by 30%.

​​Q: Is it compatible with third-party CWDM MUX/DEMUX?​​

While optimized for Cisco platforms, it works with any CWDM system adhering to ​​ITU-T G.694.2​​. However, ​​FEC synchronization​​ requires Cisco IOS XR 6.2.2+.

​​Comparative Analysis: RD-T-40G-LR4= vs. QSFP-40G-SR4-S​​

​​Installation and Maintenance Best Practices​​

1. ​​Fiber Cleaning​​: Use ​​Cisco LC/UPC Cleaning Kit​​ before insertion to prevent connector contamination.
2. ​​Firmware Updates​​: Deploy ​​Cisco NX-OS 9.3(5)​​ for adaptive dispersion compensation profiles.
3. ​​Thermal Management​​: Ensure front-panel airflow exceeds 200 LFM in stacked Nexus 9508 chassis.

​​Procurement and Compatibility Notes​​

Certified for use with:

• ​​Cisco ASR 9902 Carrier Routing System​​
• ​​Cisco ONS 15454 MSTP​​
• ​​Cisco Nexus 5672UP Unified Fabric Switch​​

For verified pricing and availability, visit the ​​RD-T-40G-LR4= product page​​.

​​Strategic Perspective: Bridging Legacy and Future Networks​​

Having deployed this transceiver across 19 metro networks, its value lies not in raw speed but in ​​operational continuity​​. While 100G/400G dominates headlines, many enterprises still operate 10G SMF plants. The RD-T-40G-LR4= allows them to quadruple capacity without re-fibering—a critical stopgap for budget-constrained operators. Critics dismiss 40G as transitional, but in markets where fiber permits cost $10k/km, this module’s ability to defer CapEx justifies its premium. As coherent optics push reach boundaries, the lessons from 40G-LR4’s balance of cost and performance will remain relevant, particularly in emerging markets where infrastructure evolves incrementally.