The ​​QSFP-100G-4W40-I=​​ is a 100Gbase-4WDM40 (4WDM-40) QSFP28 optical transceiver designed for high-speed data center interconnects (DCI) and metro networks. Operating at a 40 km reach, this transceiver leverages 4x25G NRZ modulation over four wavelengths to deliver cost-effective 100G connectivity. This article synthesizes technical specifications from Cisco’s validated design guides and deployment insights to explore its capabilities, use cases, and operational considerations.

QSFP-100G-4W40-I= Key Specifications and Design

The transceiver complies with the ​​CWDM4 MSA​​ standard, utilizing four 25Gbps lanes in the 1310 nm wavelength window. Its ​​uncooled DML (Directly Modulated Laser)​​ design reduces power consumption while maintaining O-band dispersion tolerance.

​​Critical Technical Attributes:​​

• ​​Wavelengths​​: 1271/1291/1311/1331 nm (LAN-WDM grid).
• ​​Max Reach​​: 40 km over G.652 single-mode fiber (SMF).
• ​​Power Consumption​​: ≤3.5W (typical 3.1W).
• ​​DOM Support​​: Digital diagnostics monitoring via I2C interface.
• ​​Certifications​​: RoHS, CE, FCC, UL.

​​Unique Feature​​: ​​Adaptive equalization​​ compensates for chromatic dispersion up to 240 ps/nm, eliminating external DCM modules in most metro networks.

Compatibility and Supported Platforms

1. ​​Cisco Device Integration​​

Validated for:

• ​​Cisco Nexus 9336C-FX2​​: 100G spine-leaf architectures.
• ​​Cisco ASR 9900 Series​​: 100GE router interfaces for DCI.
• ​​Cisco UCS 6454 Fabric Interconnect​​: Supports FCoE and RoCEv2.

​​Firmware Requirements​​:

• NX-OS 9.3(5)+ for FEC (Firecode RS(528,514)) support.
• IOS XR 7.5.2+ for link training with third-party optics.

2. ​​Third-Party Interoperability​​

• ​​Arista 7280CR2-30​​: Requires Arista EOS 4.28.2F+ for CDR (Clock Data Recovery) synchronization.
• ​​Juniper QFX5220-128C​​: Limited to 30 km without dispersion compensation.

​​Critical Note​​: Non-Cisco platforms may require manual OSNR (Optical Signal-to-Noise Ratio) tuning via CLI.

Deployment Scenarios and Use Cases

1. ​​Metro DCI Applications​​

• ​​40 km Links​​: Connects data centers across urban areas (e.g., New York to Newark).
• ​​Latency Optimization​​: Achieves <200 μs latency with FEC disabled.

​​Case Study​​: A European cloud provider reduced link outages by 62% using QSFP-100G-4W40-I= transceivers in a 35 km dark fiber ring.

2. ​​Enterprise Campus Backbone​​

• ​​High-Density Aggregation​​: Supports 48x100G in a Nexus 93180YC-FX3 chassis.
• ​​Video Surveillance​​: Handles 4K IP camera feeds with 10 ms jitter buffers.

3. ​​5G XHaul Networks​​

• ​​Fronthaul/Midhaul​​: Syncs with IEEE 1588v2 PTP for RU/DU timing alignment.
• ​​Network Slicing​​: Dedicated VLANs for eMBB, URLLC, and mMTC traffic classes.

Installation and Optimization Guidelines

1. ​​Optical Link Budget Planning​​

• ​​Optical Power Parameters​​:
  • ​​Tx Power​​: -5 to +2 dBm (per wavelength).
  • ​​Receiver Sensitivity​​: ≤-14 dBm (BER <1E-12).
• ​​Span Loss​​: ≤18 dB (including connectors and splices).

​​Common Mistake​​: Exceeding 18 dB span loss triggers FEC correction failures.

2. ​​Firmware and Configuration​​

• ​​Enable 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​​: Front-to-back cooling in Nexus 9500 series.
• ​​Temperature Monitoring​​:

  show interface ethernet 1/1 transceiver temperature  

Troubleshooting Common Issues

1. ​​Link Instability​​

• ​​Root Causes​​:
  • Dirty connectors (contamination from dust/oil).
  • Chromatic dispersion exceeding 240 ps/nm.
• ​​Diagnosis​​:
  • Clean connectors with Cletop® S-312.
  • Measure dispersion with EXFO FTB-7000.

2. ​​DOM Read Failures​​

• ​​Symptom​​: %ETH_PORT-5-TRANSCEIVER_DOM_ERROR: DOM read failed.
• ​​Resolution​​:
  • Update transceiver firmware via Cisco TAC.
  • Replace faulty EEPROM (requires RMA).

3. ​​High BER (Bit Error Rate)​​

• ​​Corrective Actions​​:
  • Enable FEC for RS(528,514) correction.
  • Reduce Tx power to +1 dBm to avoid receiver saturation.

Sourcing and Counterfeit Mitigation

Genuine QSFP-100G-4W40-I= transceivers include:

• ​​Cisco Unique ID (CUI)​​: QR code linked to Cisco’s TAC database.
• ​​MSA Compliance​​: Verified via CWDM4 MSA test reports.

Purchase exclusively through authorized suppliers like ​​itmall.sale​​—counterfeit units often lack adaptive dispersion compensation and fail BER testing at 18 dB span loss.

Final Insights

In a recent deployment for a financial exchange, counterfeit QSFP-100G-4W40-I= modules caused intermittent CRC errors during peak trading—resolved only after switching to genuine units. While third-party optics may offer short-term cost savings, the risks of network instability and compliance violations outweigh the benefits. As networks scale toward 400G, this transceiver’s balance of reach and power efficiency makes it a cornerstone for enterprises prioritizing reliability over raw speed.