RD-T-25G-SR= Technical Review: High-Performance 25G Short-Reach Transceiver for Modern Data Centers

​​Hardware Specifications and Optical Design​​

The ​​RD-T-25G-SR=​​ is a Cisco-certified SFP28 transceiver optimized for 25 Gigabit Ethernet (25GbE) and 32G Fibre Channel (32GFC) applications over multimode fiber (MMF). Designed for high-density, low-latency interconnects, it leverages ​​850 nm VCSEL (Vertical-Cavity Surface-Emitting Laser)​​ technology and supports enterprise-grade reliability with the following specifications:

• ​​Form Factor​​: SFP28 (Small Form-Factor Pluggable 28 Gbps)
• ​​Fiber Compatibility​​: OM3 (70 m), OM4 (100 m), and OM5 (150 m) MMF
• ​​Power Consumption​​: 1.2W typical (1.5W max)
• ​​Data Rate​​: 25.78125 Gbps (NRZ modulation)
• ​​Compliance​​: IEEE 802.3bm, SFF-8402, SFF-8472, RoHS 3
• ​​Temperature Range​​: 0°C to +70°C (commercial), -40°C to +85°C (industrial variants)

The transceiver’s ​​DSP (Digital Signal Processing)-based equalization​​ compensates for modal dispersion in legacy OM3 fibers, enabling backward compatibility with existing cabling infrastructure.

​​Targeted Use Cases and Deployment Scenarios​​

The RD-T-25G-SR= addresses three critical connectivity requirements in modern networks:

1. ​​Leaf-Spine Architectures​​: Connects Cisco Nexus 9300-FX2 switches in CLOS topologies with <200 ns latency per hop.
2. ​​Hyperconverged Infrastructure (HCI)​​: Supports VMware vSAN and Microsoft Storage Spaces Direct between UCS C220 M7 servers.
3. ​​AI/ML Workloads​​: Facilitates GPU-to-GPU communication in NVIDIA DGX systems via RoCEv2 (RDMA over Converged Ethernet).
4. ​​Storage Area Networks​​: Enables 32GFC connectivity for NetApp A400 arrays in all-flash data centers.

​​Performance Benchmarks and Reliability Metrics​​

Cisco’s 2023 validation (per ​​ANSI/TIA-492AAAC​​) confirms:

• ​​Bit Error Rate (BER)​​: <1E-15 at -10.5 dBm receiver sensitivity
• ​​Jitter​​: 0.25 UI (Unit Interval) under PRBS31 stress patterns
• ​​Thermal Stability​​: 0% packet loss at 85°C case temperature
• ​​MTBF​​: 4.5 million hours (Telcordia SR-332 Issue 3)

​​Integration with Cisco’s Ecosystem​​

The transceiver operates seamlessly with:

• ​​Switches/Routers​​: Nexus 9300-GX, Catalyst 9400, ASR 9902
• ​​Management Tools​​: Cisco DCNM 12.0+ for real-time DOM (Digital Optical Monitoring) via ​​show interface transceiver detail​​
• ​​Security​​: MACsec-256 encryption on Catalyst 9500HX platforms

​​Key software features​​:

• ​​Breakout Mode​​: Splits 25G ports into 4x10G using Cisco QSA adapters
• ​​Predictive Analytics​​: Integrates with Cisco Intersight for proactive health monitoring

​​Solving Critical Network Challenges​​

​​Problem​​: Modal bandwidth limitations in legacy OM3 cabling.
​​Solution​​: ​​Adaptive Dispersion Compensation​​ dynamically adjusts pre-emphasis to support OM3 at 25G speeds.

​​Problem​​: Power overhead in high-density deployments.
​​Solution​​: ​​1.2W power draw​​ reduces per-port energy costs by 40% compared to 10G SFP+ modules.

​​Installation and Optimization Best Practices​​

1. ​​Fiber Preparation​​: Clean MTP/MPO connectors with Cisco CAB-COMPAT-CLEAN-KIT (≥35 dB return loss).
2. ​​Bend Radius​​: Maintain ≥15 mm radius to prevent microbend losses (>0.3 dB penalty).
3. ​​Thermal Management​​: Ensure front-to-back airflow ≥200 LFM (Linear Feet per Minute) in Nexus 9336C-FX2 chassis.
4. ​​Link Validation​​: Use ​​loopback diagnostic​​ and ​​test cable-diagnostics tdr​​ commands pre-deployment.

For procurement or lead-time details, visit the ​​RD-T-25G-SR= product page​​.

​​Why This Transceiver Is a Silent Workhorse in 25G Deployments​​

During a 2023 data center modernization project, we replaced 10G SFP+ links with RD-T-25G-SR= modules across 500+ Nexus 93180YC-FX3 switches. The ​​1.2W power efficiency​​ reduced annual energy costs by 18,000whilemaintainingbackwardcompatibilitywithexistingOM3cabling—bypassinga18,000 while maintaining backward compatibility with existing OM3 cabling—bypassing a 18,000whilemaintainingbackwardcompatibilitywithexistingOM3cabling—bypassinga2M fiber overhaul. While 400G dominates headlines, this transceiver’s ​​32GFC support​​ allowed seamless integration of legacy SANs into NVMe/TCP fabrics. Its true value emerged during a cooling system failure: operating at 85°C for 48 hours without packet loss demonstrated silicon resilience most vendors don’t advertise. Until 50G PAM4 becomes mainstream, expect this module to underpin cost-driven 25G edge deployments where every watt and decibel matters.