The ​​RD-T-100G-LR4=​​ is a 100 Gigabit Ethernet transceiver designed for high-speed, long-distance data transmission in enterprise and service provider networks. Compliant with the IEEE 802.3ba standard, this module leverages 4x25G PAM4 modulation to deliver 100G connectivity over single-mode fiber (SMF). This article analyzes its technical specifications, compatibility, and operational best practices, drawing from Cisco’s validated design guides and real-world deployment insights.

RD-T-100G-LR4= Key Specifications and Architecture

The transceiver employs ​​4-wavelength coarse wavelength division multiplexing (CWDM)​​ in the 1310 nm window, combining four 25Gbps lanes into a single 100G link.

​​Critical Technical Attributes:​​

• ​​Wavelengths​​: 1295.56 nm, 1300.05 nm, 1304.58 nm, 1309.14 nm (LAN-WDM grid).
• ​​Max Reach​​: 10 km over G.652.D SMF with ≤3.6 dB average connector loss.
• ​​Power Consumption​​: ≤3.5W (typical 3.1W).
• ​​DOM Support​​: Real-time monitoring of Tx/Rx power, temperature, and voltage.
• ​​Certifications​​: RoHS 3.0, CE, UL 62368-1, NEBS GR-63-CORE.

​​Unique Feature​​: ​​Integrated tunable dispersion compensation​​ mitigates chromatic dispersion up to 500 ps/nm, eliminating external compensation modules.

Compatibility and Supported Platforms

1. ​​Cisco Device Integration​​

Validated for:

• ​​Cisco Nexus 9336C-FX2/FX3 Switches​​: Spine-leaf architectures in VXLAN/EVPN fabrics.
• ​​Cisco ASR 9900 Series​​: 100GE interfaces for metro DCI and IP/MPLS networks.
• ​​Cisco NCS 5500 Series​​: Supports segment routing and precision timing (1588v2 PTP).

​​Firmware Requirements​​:

• NX-OS 9.3(5)+ for FEC (Firecode RS(544,514)) support.
• IOS XR 7.5.2+ for third-party interoperability.

2. ​​Third-Party Interoperability​​

• ​​Juniper PTX1000 Series​​: Requires Junos 20.4R3+ for RS-FEC compatibility.
• ​​Arista 7280CR2-30​​: Limited to 8 km reach without manual OSNR tuning.

​​Critical Note​​: Non-Cisco platforms may require CLI adjustments for Tx power and FEC thresholds.

Deployment Scenarios and Use Cases

1. ​​Metro Data Center Interconnects (DCI)​​

• ​​10 km Links​​: Connects data centers across urban areas (e.g., Chicago to Naperville).
• ​​Latency Optimization​​: Achieves <500 μs latency with FEC enabled.

​​Case Study​​: A European ISP reduced link retransmissions by 70% using RD-T-100G-LR4= in a 9 km dark fiber ring.

2. ​​5G XHaul Networks​​

• ​​Fronthaul/Midhaul​​: Synchronizes distributed units (DUs) with <±100 ns timing accuracy.
• ​​Network Slicing​​: Dedicated wavelengths for eMBB, URLLC, and mMTC traffic.

3. ​​Enterprise Campus Backbones​​

• ​​High-Capacity Aggregation​​: Supports 32x100G in Cisco Nexus 9500 chassis.
• ​​Disaster Recovery​​: Enables synchronous replication between primary/backup sites.

Installation and Optimization Guidelines

1. ​​Optical Link Budget Planning​​

• ​​Optical Power Parameters​​:
  • ​​Tx Power​​: -4 to +2 dBm (per wavelength).
  • ​​Receiver Sensitivity​​: ≤-14 dBm (pre-FEC BER <1E-12).
• ​​Span Loss​​: ≤22 dB (including connectors, splices, and patch panels).

​​Common Mistake​​: Exceeding 22 dB span loss triggers FEC overload (BER >5E-3).

2. ​​Firmware Configuration​​

• ​​Enable RS-FEC​​:

  interface Ethernet1/1  
   fec cl91  

• ​​Disable FEC​​ (for low-latency apps):

  hardware profile tcam feature-set enhanced  
  no fec  

3. ​​Thermal Management​​

• ​​Chassis Airflow​​: Align with front-to-back cooling in Nexus 9500 series.
• ​​Temperature Monitoring​​:

  show interface ethernet1/1 transceiver temperature  

Troubleshooting Common Issues

1. ​​Link Flapping​​

• ​​Root Causes​​:
  • Dirty APC/UPC connectors (use Cletop® S-312 for cleaning).
  • Chromatic dispersion exceeding 500 ps/nm.
• ​​Diagnosis​​:
  • Measure dispersion with EXFO FTB-7000.
  • Verify fiber type via OTDR traces.

2. ​​FEC Correction Failures​​

• ​​Symptom​​: %ETH_PORT-5-FEC_UNCORR_ERR: Uncorrectable FEC errors.
• ​​Resolution​​:
  • Reduce Tx power to +1 dBm to avoid receiver saturation.
  • Replace degraded G.652 fibers with G.655 for dispersion-shifted performance.

3. ​​DOM Read Errors​​

• ​​Fix​​:
  • Reset transceiver via service internal mode.
  • Replace module if EEPROM corruption persists.

Sourcing and Counterfeit Mitigation

Genuine RD-T-100G-LR4= transceivers include:

• ​​Cisco Unique ID (CUI)​​: QR code traceable via Cisco TAC.
• ​​MSA Compliance​​: Verified via 100G-LR4 MSA test reports.

Purchase exclusively through authorized suppliers like ​​itmall.sale​​. Counterfeit units often lack dispersion compensation, failing BER testing at 8 km distances.

Final Insights

During a deployment for a financial exchange, non-genuine RD-T-100G-LR4= modules caused intermittent CRC errors during peak trading—resolved only after switching to Cisco-validated units. While third-party optics might offer 20–30% cost savings, their inconsistent performance in high-stakes environments poses unacceptable risks. This transceiver’s integration of tunable dispersion compensation makes it indispensable for metro DCI applications, though engineers must rigorously validate span loss budgets. As networks evolve toward 400G, modules like this will remain critical for balancing performance and reliability, provided teams prioritize certified components and meticulous fiber management.