Application Note

Why Do I Need To Inspect And/Or Clean The Fiber In An Optical BBU/RRH Link?

Source: Anritsu Company

After ruling out traditional problems like passive intermodulation (PIM), poorly aimed antennas and/or other coaxial problems, dirty fiber connectors account for 60 to 75% of the alarms, failures, and poor throughput problems found in modern cellular systems today. It has been several years since the initial introduction of the current BBU (Baseband Unit) and RRH (Remote Radio Head) architecture of today’s wireless cellular systems. Conceptually the architecture is ideal and has very few drawbacks, although in early deployments many problems were encountered with this type of architecture. In the earliest deployments of these systems, many field technicians were not familiar with the new optical interface and simply did not have the required experience to properly install, and/or troubleshoot and resolve the issues on site, which led to the brute force replacement of many early deployed RRH units. There is sufficient evidence supporting the fact that many of these replaced RRH units were determined to have no faults found after being returned to the manufacturer. So what really happened? In this article we will take a closer look at the actual physical optical link and we will discuss the optical transceiver hardware that is most commonly used in this type of system.