Page 361 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

FIGURE 13.28
Connector examples: (a) ST and (b) SC connectors.
3. Reliability
4. Fiber internal reflective properties
5. Ease of termination
6. Cost
Both the splice and the connector are subject to a range of transmission issues inducing optical
losses across the junction between the two fibers. These issues are practically all mechanical in nature whereby there is a mismatch of optimal fiber end-to-end mating. The mating should be as close as possible to a perfect end-to-end matching with clean and clear end-caps, but in practice a combination of contaminants, less-than-parallel end points, and fiber size mismatch cause a host of losses, as shown in Figure 13.29.
Cable splicing and connector mating are quite simple and reliable, once proper training and practice are received. It is highly recommended to take a basic hands-on fiber termination course on the nuances of fiber terminations. The connection process, while simple, is quite unforgiving for lack of attention to detail.
13.2.5.2 Pay attention—this part is important!
The total power loss through the conductive medium (fiber/connector/splice/etc.) versus the optical power input is its “optical power budget” (Figure 13.30). As a rule of thumb in the ROV industry (based upon the industry standard Focal Technologies 900-series fiber-optic multiplexer’s power budget), a signal loss of less than 20 dB between the optical transmitter and receiver will be sufficient for data transmission—that is, above (greater than) 20 dB loss, a typical fiber-based ROV system will begin experiencing telemetry and sensor losses due to exceeding the optical power budget.
13.2 Transmission 353