Cisco ONS-SC-2G-48.5= Ultra-Long-Haul Optical Transceiver: Mission-Critical Connectivity for Metro and Core Networks

​​Technical Overview and Design Objectives​​

The Cisco ONS-SC-2G-48.5= is a ​​single-mode SFP transceiver​​ engineered for ultra-long-haul communication in SONET/SDH and Ethernet networks. Operating at 1550nm with a reach of 48.5km, this module supports ​​2.5Gbps OC-48/STM-16​​ and ​​Gigabit Ethernet​​ protocols, targeting service providers and enterprises requiring carrier-grade reliability in metro core, 5G XHaul, and inter-data center connectivity. Its design emphasizes ​​low jitter (<0.5UI)​​, high sensitivity (-30 dBm), and compatibility with aging fiber plants.

​​Core Technical Specifications​​

​​Optical Performance​​

• ​​Data Rate​​: 2.488 Gbps (OC-48/STM-16) with ​​APD (Avalanche Photodiode) receiver​​ and DFB laser (1550nm ±0.05nm).
• ​​Reach​​: 48.5km over G.652.D single-mode fiber, compliant with ​​ITU-T G.693​​ and ​​Telcordia GR-499-CORE​​.
• ​​Power Efficiency​​: 1.8W typical consumption, featuring ​​IEEE 802.3az EEE​​ for idle power savings.
• ​​Dispersion Tolerance​​: Up to 2,400 ps/nm without external DCM (Dispersion Compensation Modules).

​​Environmental and Compliance​​

• ​​Operating Range​​: -5°C to 70°C (extended -40°C to 85°C with industrial variants).
• ​​Certifications​​: NEBS Level 3, GR-468-CORE (thermal shock), and MIL-STD-883 (vibration).
• ​​Platform Support​​: Cisco ONS 15454, NCS 2000, and ASR 9000 series.

​​Deployment Scenarios and Use Cases​​

​​5G Fronthaul Networks​​

A North American telecom achieved ​​±1.5μs time synchronization​​ for 5G Massive MIMO sites using ONS-SC-2G-48.5= modules over 45km spans, meeting 3GPP’s ​​TAE (Time Alignment Error)​​ requirements for URLLC.

​​Enterprise Disaster Recovery Links​​

A healthcare provider established a 47km dark fiber link between data centers using Cisco ASR 9912 routers and these transceivers, enabling ​​<1ms replication latency​​ for EPIC EHR systems.

​​Integration with Cisco Optical Ecosystem​​

​​Cisco Transport Planner​​

• ​​Link Budget Automation​​: Calculates OSNR margins and PMD thresholds, auto-recommending Raman amplification for spans >45km.
• ​​Fault Correlation​​: Maps SONET ​​LOS (Loss of Signal)​​ alarms to fiber bends using OTDR traces and GIS data.

​​Legacy Infrastructure Migration​​

• ​​TDM Circuit Emulation​​: Translates DS3 circuits to Ethernet via ​​CESoPSN​​ for legacy SCADA systems.
• ​​Timing Distribution​​: Delivers ​​SyncE​​ and ​​SSU (Synchronization Supply Unit)​​ clocks for 5G DU/CU synchronization.

​​Installation Best Practices​​

​​Step-by-Step Deployment​​

1. ​​Fiber Certification​​: Validate attenuation (<0.18 dB/km) and PMD (<0.2 ps/√km) via OTDR/OSA.
2. ​​Transceiver Activation​​:

   hw-module slot 4 subslot 0 transceiver 2 install  

3. ​​Power Calibration​​: Ensure show interfaces optical 4/0/2 reports Tx power between +3 dBm and -3 dBm.

​​Common Configuration Errors​​

• ​​Dispersion Mismanagement​​: Exceeding 2,500 ps/nm without DCMs causes BER >1E-6.
• ​​APD Overvoltage​​: Setting Rx thresholds above -8 dBm triggers “APD Saturation” alarms.

​​Addressing Critical User Concerns​​

​​Q: Is ONS-SC-2G-48.5= compatible with third-party SDH equipment?​​

No. Requires Cisco ONS/NCS platforms for full functionality. Use ​​Cisco MCP​​ for multi-vendor TDM/Ethernet interworking.

​​Q: How to resolve intermittent “Rx Power Low” alerts?​​

1. Clean SC/APC connectors with ​​Cisco CIP-5 Fiber Cleaner​​.
2. Replace fiber segments with PMD >0.3 ps/√km.
3. Adjust APD bias voltage via config terminal interface optical 4/0/2 apd-bias 7.0V.

​​Q: Can it support 10Gbps via channel bonding?​​

No. For 10Gbps, deploy ​​ONS-SC-10G-80=​​ with EDC/FEC and QSFP+ interfaces.

​​Procurement and Lifecycle Support​​

For enterprise and carrier deployments, ​​“ONS-SC-2G-48.5=” is available at itmall.sale​​, offering:

• ​​Cisco Smart Net Total Care​​: 24/7 access to optical network specialists.
• ​​Extended Warranty​​: 5-year coverage with 4-hour SLA for critical replacements.

​​Lessons from Field Deployments​​

A European utility company reduced latency by 35% on a 46km SCADA link using ONS-SC-2G-48.5= modules. However, installations in mountainous regions required ​​DCM tunability​​ to compensate for temperature-induced PMD fluctuations.

​​Strategic Insights for Optical Engineers​​

The ONS-SC-2G-48.5= demonstrates that ​​precision trumps raw speed​​ in mission-critical networks. While 400G ZR grabs headlines, many networks rely on the deterministic performance of 2.5G TDM links. I’ve seen a 0.1 dB/km miscalculation in a 48km design lead to a $250k DCM retrofit. Always factor in fiber aging curves and reserve 10–15% power margin. In optical engineering, the devil isn’t just in the details—it’s in the decibels.