Principle of RFTS and System Configuration

RFTS is based on Optical Time Domain Reflectometry (OTDR). OTDR itself is a mature technology but SEI has integrated this technology together with field assembly connector including termination filter. RFTS is used in the wavelength from 1580nm through 1680nm. In the FTTx, actual data signal and 10G PON uses different wavelengths. (FTTx: 1310/1490/1550nm, 10G: 1260-1280/1574-1580nm) The most important function of RFTS is finding the faulty point.

Currently, SEI proposes three ways of detecting the faulty point. One way is the high reflection wherein the reflection level of the termination filter point is measured. Second is the wavelength marking in which the system is combined tunable OTDR and termination filter with wavelength marker. Third is the wavelength routing wherein the system is integrated tunable OTDR with wavelength router. The third one is the best solution but the system cost is slightly expensive. So, appropriate selection is based on target service level.

RFTS system is consisted of Remote Test Unit (RTU), Test Access Module (TAM), Termination Filter (TF), and Test System Controller (TSC). The alarm output has a very user-friendly interface and it is possible to send those messages to mobile phone by email, if required by the customer. The sample monitor display of TSC and alarm information is shown in the following figure.

SEI now realizes around 20cm of ultra-high resolution RFTS using the state of the art technology'Optical Coherence Domain Reflectometry (OCDR). OCDR realizes the ultra-high resolution by means of the interference between the original optical source and reflected optical signal.

Effectiveness of RFTS

There are lots of problem in the real field. For example, various constructions happen every day and some constructors may miss-judge or be ignorant of the place of the optical cable and accidentally cut it. Another one is natural disasters, like typhoons, hurricane, earthquake, heavy snow etc. And another one is biological damage. Sometimes biological creatures are taking unexpected actions, like biting cable, depositing eggs in cable. And what is even worse is the inappropriate working of mechanical splice. With this type of trouble, it is very hard to find the real cause and it takes a long time to understand the behavior of faulty condition. Anyway, if RFTS is deployed, those troubles are easy to solve because ease of finding the exact point and then enable quick recovery.

Figure 3 shows the field data that came from an operator in Japan. This operator has received 69 cases of trouble in a month and 8 cases in those are related outside plant. And if you integrate RFTS with the current network management system (NMS), 12 no problem cases of are also very easy to solve and satisfy the customer quickly. So total 25 cases (8+5+12), around 36 percent of the total trouble tickets, could be handled faster by using RFTS.

This article describes various benefits of RFTS but if considering only the first stage (CAPEX), RFTS is expensive for the initial investment. The most important thing about designing the network is TCO (total cost of ownership) and especially running cost including maintenance. I believe that the readers really understand this point and consider installing RFTS on their site in the near future. After installing RFTS, they might find out the usefulness and cost-effectiveness easily. And SEI will continue to improve the functions and realize the customer requirements within the product life cycle of RFTS.