Time to Focus on Fiber in HFC
In the world of test measurements, much of the cable industry focus has been directed towards the biggest challenges, namely the coaxial side of the HFC network. With the great progress cable has made in this space, it is now time for the industry to zero in on the fiber side of the network. Increasing bandwidth demands are requiring many operators to move to a fiber deep deployment scheme. One popular method is converting to a radio frequency over glass (RFoG) design. RFoG allows operators to replace the coax portion of the HFC network with fiber, resulting in a FTTH network while maintaining the same equipment in hubs and headends. Even though fiber is less susceptible to interference as coax, it still requires an appropriate set of testing procedures, test equipment and a skilled workforce in order to measure performance and maintain uptime, especially considering the higher expectations of today’s customers. Most of the existing testing procedures -- even the SCTE's own Measurement Recommended Practices for Cable Systems -- assume the operator has an HFC design and concentrate on the coax portion of the network. While the optical side is taken into consideration during routine testing, it does not reflect updates in optical testing and equipment. One example of this comes during upstream plant setup or routine adjustment in an HFC design. During this process, the procedures indicate this as an ideal time to test the fiber for amplitude flatness but do not provide the processes or equipment required for such a test. Other concerns, such as driving more bandwidth through RFoG using DWDM, require maintaining extremely tight frequency constraints in order to reduce interference from dispersion that may led to bit errors or optical beat interference (OBI). To monitor this, it is important for field technicians to be familiar with optical test instruments and measurement techniques. One way to ensure the knowledge is available is by updating the industry’s test measurement guidelines. Among the needs being identified by SCTE: determining which optical measures are best suited for testing for metrics, such as fiber phase/group delay, optical return loss, power and signal leakage; educating the industry on the function and use of optical spectrum analyzers, optical power meters, optical time-domain reflectometers, optical loss test sets and other fiber optic tools and equipment; and increased availability of instructional material that can drive adoption of optimal testing practices. Cable literally has set the standard for test and measurement in HFC. With the increased use of RFoG and other FTTH architectures, it is essential that SCTE and the industry ensure that the same level of attention is paid to optical fiber plant. — Travis Murdock, Standards Administrator, the Society of Cable Telecommunications Engineers (SCTE) This is the latest installment of "Technically Speaking with SCTE," a monthly blog of interviews and columns to provide Light Reading Cable readers with timely updates on the SCTE's initiatives and activities.