In order to successfully test the FTTA installation, all individual components should be tested separately and then tested as a system or subsystem to ensure that all important components of the system achieve their best performance. Careful planning of the FTTA test process is particularly important, as the installation may be completed in discrete stages.

A basic requirement of fiber optic cable performance is cleanliness, and the best way to complete cleanliness verification is inspection. Check the connector ceramic ferrule for scratches under a fiber optic microscope. Similarly, the fiber core and coating layer should be amplified and tested to ensure that they are clean and undamaged. If dust or contamination is found, the connection surface can be cleaned and then re-tested until the acceptance criteria for use are reached.

After ensuring the cleanliness of each connection point, the continuity and insertion loss of each cable laid should be tested before installation. The Visual Fault Locator (VFL) tool is very suitable for verifying the continuity and integrity of the fiber.

Just like cables, RRH and BBU should be tested separately before system testing. Before installing active equipment in the tower, it is wise to check the power level of the equipment.

An Optical Time Domain Reflectometer (OTDR) is an instrument used to create a virtual "picture" of the laid fiber optic cable. The OTDR can provide important information about the integrity of the optical fiber and any connection points and splice points along the laid cable. OTDR is a single-ended tool that can be used to verify cable integrity and troubleshoot the laying of FTTA cables, thereby minimizing the number of additional tower climbs.

OTDR used to be mainly used for long-distance applications, but now it can be used to diagnose shorter-distance optical fiber laying related to FTTA. During construction, you can also use a 10-20m transmission cable to measure the loss and reflection coefficient in RRH and BBU separately through OTDR. OTDR can then become a very useful tool for maintenance activities to ensure that the overall loss and reflection coefficient of each connector remain stable and within acceptable limits.

Both coaxial and optical cables are used in FTTA base stations. Although the role of coaxial cables has now been simplified to a short jumper between the RRH and the antenna, in order to conduct a comprehensive base station verification, return loss or voltage standing wave is still required Ratio (VSWR), fault point distance and radio frequency transmission power testing; moreover, for fiber-based feeders, optical and fiber indicators including optical transmission power, and fiber inspection testing are very important. In addition to conformance testing related to signal integrity (including radio frequency characteristics), in order to ensure the quality of FTTA service, interference analysis and modulation quality are also essential.

Since all radio frequency information is now transmitted between RRH and BBU via optical fiber, test solutions that support RF over CPRI (RFoCPRI) technology can demap radio frequency components from CPRI. RFoCPRI technology can verify CPRI control signals and extract user plane traffic or radio frequency (IQ) data transmitted between the BBU and RRH, while allowing interference on mobile devices (uplink) and wireless signals (downlink). Performance is monitored and analyzed.

RFoCPRI provides the ability to understand and map user plane data and analyze it, thereby allowing RF maintenance and troubleshooting on the ground through fiber coupling at the BBU. This technology has several significant advantages, including:

·Reduce the number of times you need to climb the base station tower to a minimum, improving safety

· Minimize the number of test instruments required

· Significantly shorten maintenance time and reduce operating expenses

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