1.0 Executive Summary

This document provides a technical analysis of a request to establish a 1-Gigabit Ethernet network connection between two buildings separated by approximately 140 meters. It evaluates an initial proposal involving extended copper Ethernet and presents a comprehensive, best-practice alternative utilizing fiber optic technology. The recommended solution ensures superior performance, reliability, electrical safety, and future scalability, aligning with established industry standards for inter-building network links.

2.0 Analysis of the Technical Problem and Initial Proposal

The core technical challenge is to bridge a 140-meter gap between a main building with a server room and a remote building requiring network services for a single PoE IP camera and a VoIP phone. An existing 2-inch underground conduit is available for cabling.

2.1 Stated Requirements:

• Distance: 140 meters (approx. 460 feet).
• Bandwidth: Minimum 1 Gbps.
• Services: Power over Ethernet (PoE) for end devices in the remote building.
• Physical Path: Existing underground conduit.

2.2 Initial Proposed Solution:
The initial plan detailed in the source material suggests using a standard copper Ethernet cable, interrupted mid-span by a PoE-powered Ethernet extender. This extender would be housed in a waterproof enclosure within a manhole at the 70-meter mark and would be responsible for regenerating the signal and passing PoE through to the end devices.

2.3 Critical Evaluation:
While creative, this copper-based solution introduces significant technical risks and is not a recommended design:

• Violation of Ethernet Standards: The 1000BASE-T standard specifies a maximum channel length of 100 meters. A 140-meter run, even with an extender, is non-compliant and highly susceptible to signal degradation, attenuation, and crosstalk, which will result in packet loss, high latency, and intermittent link failure.
• Reliability and Environmental Concerns: Placing active electronics (the extender) in an underground manhole creates a critical single point of failure. Despite a waterproof box, this equipment is exposed to extreme temperature fluctuations, humidity, and potential water ingress, drastically reducing its operational lifespan and reliability.
• Electrical Hazard: Running copper cabling between buildings with separate electrical grounds creates a conductive path. This exposes network equipment in both buildings to severe damage from ground potential differences and, more critically, from nearby lightning strikes inducing high-voltage surges on the cable.
• Limited Scalability: The solution is purpose-built for only two devices. Adding more devices in the remote building would require more complex and failure-prone extender arrangements.

3.0 Recommended Best-Practice Solution: Fiber Optic Interconnect

The industry-standard and most robust solution for this scenario is the deployment of a fiber optic link. Fiber optic cable is the definitive choice for inter-building connectivity as it is immune to electromagnetic interference (EMI) and electrical surges, supports vastly higher bandwidth, and operates reliably over distances far exceeding 140 meters.

3.1 Bill of Materials and Architecture:

1. Cabling: Single-Mode Fiber (SMF) Optic Cable (OS2, 2-4 strand minimum). While Multimode Fiber (MMF) would suffice for this distance, SMF offers virtually unlimited bandwidth scalability for future needs and is often competitively priced. Using pre-terminated or armored fiber can simplify installation and enhance physical durability within the conduit.
2. Transceivers: Two (2) 1000BASE-LX/LH Small Form-factor Pluggable (SFP) modules. The Cisco GLC-LH-SMD is the standard part number for this application, supporting 1 Gbps up to 10 km over SMF.
3. Main Building Equipment: An existing switch with an available SFP port (e.g., Cisco Catalyst 9200/9300 Series).
4. Remote Building Equipment: A compact PoE-capable switch. A model such as the Cisco Catalyst 1000 Series (C1000-8P-2G-L) is ideal. This provides:
   • An SFP uplink port for the fiber connection.
   • Multiple PoE/PoE+ access ports for the camera, phone, and future devices.
   • A stable, managed platform for troubleshooting and configuration.
5. Termination: Two (2) fiber optic patch panels or enclosures to provide a secure and professional termination point for the fiber cable in each building.

3.2 Implementation Topology:

• Step 1: The SMF cable is pulled through the existing 2-inch conduit.
• Step 2: In each building, the fiber is terminated into a wall-mounted fiber patch panel.
• Step 3: In the main building, a GLC-LH-SMD SFP is inserted into the core switch. A fiber patch cord connects the SFP to the patch panel.
• Step 4: In the remote building, the Cisco Catalyst 1000 compact switch is installed. A second GLC-LH-SMD SFP is inserted into its uplink port and connected via patch cord to the local fiber panel.
• Step 5: The IP camera and VoIP phone are connected to the PoE ports on the Catalyst 1000 switch.

4.0 Conclusion

By deploying a fiber optic link and a compact PoE switch in the remote building, all technical requirements are met with a solution that is secure, reliable, and scalable. This design eliminates the risks associated with an out-of-spec copper run, protects expensive network equipment from electrical damage, and provides a stable foundation for future network growth in the remote building. This approach represents Cisco’s recommended best practice for inter-building campus network design.