100km optical modules are designed for long-distance single-mode fiber transmission, typically operating at 1550nm with advanced optical amplification and monitoring capabilities.

Overview

100km optical modules, such as QSFP28 100G ZR4 or SFP 1550nm ZX100, are engineered for long-haul optical communication, including backbone networks, inter-city links, and data center interconnects . These modules overcome fiber attenuation and dispersion challenges by using low-loss wavelengths (1550nm), optical amplifiers, and sometimes coherent detection to maintain signal integrity over 100 kilometers .

Key Measurement Parameters

1. Wavelength and Fiber Type
   • Operate primarily at 1550nm, which has the lowest attenuation (~0.19dB/km) in standard single-mode fiber (G.652) for long-distance transmission .
   • Compatible with single-mode fiber (SMF) using LC connectors for duplex or simplex connections .
2. Optical Power and Link Budget
   • Transmit power is carefully calibrated to compensate for fiber loss, typically around 0.35dB/km for standard SMF .
   • Modules may include pre-amplifiers or semiconductor optical amplifiers (SOAs) to boost weak signals at the receiver end .
3. Data Rate and Modulation
   • QSFP28 modules support 100Gbps using 4-lane 25G LAN WDM multiplexing.
   • Coherent modules can extend beyond 100km by using phase and polarization modulation combined with digital signal processing (DSP) to correct chromatic and polarization mode dispersion .
4. Bit Error Rate (BER) and Signal Quality
   • Typical measurements are performed at BER ≤ 1E-12 using PRBS test patterns (e.g., 2^31-1) to ensure reliable transmission .
   • Extinction ratio (ER) and optical signal-to-noise ratio (OSNR) are monitored to maintain signal integrity over long distances.
5. Digital Optical Monitoring (DOM)
   • Modern 100km modules include DOM via I2C interface, allowing real-time monitoring of temperature, voltage, optical power, and laser bias current .
   • This ensures proactive management and early detection of performance degradation.

Practical Considerations

• Insertion Loss: The actual achievable distance depends on fiber quality and splices; 100km is specified for typical fiber loss of 0.35dB/km .
• Amplification: For distances beyond 80–100km, EDFA or coherent detection may be required to maintain BER and OSNR .
• Deployment: Ideal for backbone networks, metropolitan interconnects, and data center links where intermediate repeaters are impractical .

Summary

Measuring and evaluating a 100km optical module involves checking wavelength, optical power, BER, ER, OSNR, and DOM parameters under standard single-mode fiber conditions. QSFP28 and SFP modules designed for 100km transmission combine advanced optical design, amplification, and monitoring to ensure reliable high-speed data transfer over long distances .