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Avoiding pitfalls with best practices for Fiber-Optic testing in RFoG networks

Among the many choices for multiple system operators (MSOs) to reach subscribers with fiber – such as Ethernet passive optical networks (EPON), gigabit passive optical networks (GPON), and next-generation passive optical networks (NG-PON) – there is one technology that might be overlooked but which remains viable to reach customers with fiber while maintaining an RF signal. Radio frequency-over-glass (RFoG) utilizes existing infrastructure and leverages proven, mature testing tools and expertise previously developed for the fiber to the home (FTTH) market. RFoG’s deep-fiber network design replaces the coax portion of the hybrid fiber coax network with a single-fiber PON. Downstream and return-path transmission use different wavelengths to share the same fiber, delivering cost savings and readily enabling new service turn-up.

However, there are factors to be considered when deploying an RFoG network. By following best practices during construction, installation, and turn-up, MSOs can achieve significant savings in the long run and ensure successful deployment and trouble shooting.

Network threats and testing challenges

A recent EXFO service provider survey revealed that 80 percent of deployed fiber-optic networks have had issues resulting from dirty connectors, constituting the number-one threat to fiber-optic networks. Bad connectors can seriously impact performance of a link, creating fluctuations in the laser and ultimately affecting the user experience. Every new optical connection or component represents a new point of potential failure.

RFoG networks utilize a new component in the optical distribution network – the optical splitter – which divides the signal from a single fiber into multiple outputs, reaching numerous subscribers in a point-to-multipoint system. Given that this device induces a high attenuation of the signals, proper verification must be done. Additionally, having multiple connections can generate return loss, creating fluctuations in laser power or drift. And, with multiple technologies and wavelengths travelling through the same fiber, tracking the source of failure and determining how to test can prove challenging.

Best practices for fiber-optic deployment success

Mitigating the number-one network threat of dirty connectors are fiber inspection probes, which can pinpoint and prevent network issues during the initial construction phase. As the best practice, every connector endface in the network should be cleaned and inspected during deployment. Inspection probes range from manual to fully automated, and user-friendly probes, such as EXFO’s ConnectorMax inspection probe series, feature a pass/fail LED indicator for immediate diagnosis of connector health.

Verifying wavelengths can be accomplished with a PON power meter to properly assess multiple wavelengths during the turn-up and activation phase, given the device’s ability to isolate different wavelengths. The PON power meter can measure both downstream and upstream signals when running GPON or EPON over an RFoG system, enabling technicians to test power level before leaving the site and avoiding degradation of service. EXFO’s survey reveals that 15 percent of network issues result from macrobends – a kink or bend in the fiber that can cause loss of light and signal attenuation and ultimately adversely affect end-user service – making the PON power meter a truly valuable tool.

Trouble shooting a live network requires an optical time-domain reflectometer (OTDR), which sends light into the fiber to inspect all components in the network – including every point, connector, splice and splitter – and displays results on the screen for the technician. The OTDR enables problem-solving for one customer without impacting all 32 or 64 customers supported by the same link. While OTDR technology can seem complex, EXFO’s OTDRs combine intelligence and accuracy with user-friendliness that accelerates workflow in the field. Technicians simply connect and push a button to get a green or red icon indicating where and what the problem is, enabling untrained personnel to quickly become test experts.

By leveraging effective test solutions at each stage of network implementation, MSOs can achieve optimum results with RFoG networks.

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