Bangladesh ISP's Data Centre Fiber Cabling Upgrade for 400G Network Readiness

The existing optical fiber cabling infrastructure in all three POPs had been installed incrementally over a decade, starting from 2015. The oldest sections used OM3 multimode fiber — an appropriate choice for 10GbE and 40GbE applications at the time of installation, but technically inadequate for 400GbE. IEEE 802.3bs (400GBASE-SR16 and 400GBASE-DR4+) specifies OS2 single-mode fiber for the 400GbE port types planned for the company's Cisco and Juniper equipment upgrades. The existing OM3 multimode infrastructure was therefore a physical layer barrier to the 400GbE migration, regardless of the readiness of the active equipment.

The cable management situation in all three POPs had deteriorated significantly during years of rapid network expansion. Network changes — adding new routes, installing new equipment, cross-connecting customer circuits — had been made reactively, with engineers adding fiber patch cords to existing panels without removing unused cords. The result was dense mats of fiber patch cords in the rack front areas, particularly around the high-density patch panels, creating two serious operational problems.

First, airflow. Data centre cooling efficiency depends critically on maintaining cold aisle/hot aisle airflow separation, which requires rack fronts (cold aisle) to be clear of obstructions. The accumulated fiber mats in rack front areas were blocking cold air from entering rack equipment intakes — a condition measured by SSAL's survey team as a 35°C hot spot at the air inlet of one core router chassis, compared to a 22°C ambient cold aisle temperature. This temperature elevation was within the equipment's operating spec but represented a thermal efficiency loss and a risk of accelerated equipment degradation over time.

Second, operational visibility. When a fiber patch cord runs through a dense mat of others, tracing it from one end to the other for a circuit modification or fault isolation requires removing adjacent cords — a disruptive process that has, on multiple occasions, caused accidental circuit outages when the wrong cord was removed. The company's NOC (Network Operations Centre) logged 4 unplanned outages in 18 months that were directly attributable to cable pull errors during physical layer maintenance. In a commercial ISP environment, each unplanned outage has contractual SLA implications.

Physical layer documentation was a related problem. The company's circuit database — which records what is connected to what in the physical infrastructure — had not been systematically updated for 3 years. The NOC team's accepted practice was to trace circuits physically (with a flashlight and a tone generator) rather than trusting the documentation. This approach was time-consuming during fault response and impossible to delegate to a new engineer unfamiliar with the specific POP layout.

SSAL designed and installed an OS2 single-mode fiber cabling infrastructure across all three Dhaka POPs, replacing all OM3 multimode sections, and restructured the cable management across all active rack areas.

Commscope InstaPATCH OS2 Pre-Terminated Trunk Cables: All horizontal (rack-to-rack) and vertical (rack-to-overhead tray) fiber connections across all three POPs were replaced with Commscope InstaPATCH 360 pre-terminated OS2 single-mode fiber trunk cables. The InstaPATCH system uses a modular connector system (MPO-12 multi-fiber push-on connectors at trunk breakout points, with LC-LC factory-terminated pigtails at individual port connections) that enables high-density fiber connections to be made as a single connector engagement rather than multiple individual fiber connections.

OS2 single-mode fiber supports 400GBASE-DR4+ (400GbE over single-mode fiber, using 4 x 100G wavelengths on separate fiber pairs) at distances up to 500 metres — covering all inter-rack distances within the POPs and the inter-POP dark fiber links. The Commscope OS2 fiber is low-water-peak (LWP) specification, also compatible with CWDM and DWDM applications at the POP's transponder equipment.

High-Density LC Fiber Patch Panels — 24-Port: All fiber terminations at patch panels were replaced with Commscope SYSTIMAX 360 24-port LC duplex high-density panels. These 1U panels provide 24 LC-LC duplex ports (48 fiber strands) in a single rack unit, compared to the 12-port panels they replaced — doubling the port density per rack unit and allowing the number of patch panel rack units required to be halved. The freed rack space was reallocated to active equipment or left as expansion capacity.

Each patch panel port is equipped with an LC duplex port shutter — a small spring-loaded cover that closes when the cable is unplugged, providing physical layer identification of connected versus disconnected ports and preventing fiber end contamination in the unmated port.

Cable Management Overhaul — Airflow Restoration: All existing fiber patch cords — both the new OS2 InstaPATCH connections and the retained copper patch cords for management ports — were replaced with colour-coded cables of the correct length (rather than the common practice of using excess-length cables and bundling the slack). SSAL used a Fluke cable measurement tool to calculate the required length for each connection before ordering, ensuring that patch cord lengths matched the physical routing path within 150mm.

All cables were re-routed through proper cable management arms on each rack (Panduit cable management trays were installed on racks that lacked them), and the horizontal overhead trays were re-organized with fibers segregated by circuit type (backbone, customer, management) in separate bundled groups within the tray.

Post-installation airflow measurements at the core router chassis that had measured a 35°C inlet temperature before the upgrade confirmed a post-upgrade inlet temperature of 21°C — within 1°C of the cold aisle ambient temperature, confirming that the cable management improvements had fully restored the cold aisle-to-rack intake thermal path.

Physical Layer Documentation — Commscope imVision: Commscope's imVision intelligent physical infrastructure management software was deployed to provide ongoing physical layer documentation. Each patch panel port is connected to an imVision controller that detects patch cord connections and disconnections, updating the circuit map in real time without manual documentation input. The initial as-built circuit map was created by SSAL's documentation team during the installation — recording every connection in all three POPs — and loaded into imVision as the baseline. Subsequent changes are automatically detected and logged.

The completed documentation package — imVision circuit database plus full Visio floor plan drawings of all three POPs — was delivered to the company's NOC team as part of the project handover.