|I have always been told that low magnification is used for multimode and high magnification is used for singlemode, is this true? |
Low and high magnification can benefit in inspecting both types of fiber cable. Since a core of a singlemode cable is very small, a high magnification camera is optimal for inspecting the core to see if there are any scratches, misalignments or dirt on the core. Where the benefit of a lower magnification would come in on a singlemode fiber would be particles of dust and debris residing on the outer cladding or the ferrule. It has been found that dust, dirt and contaminants can migrate from the outer edges of the fiber connector to the inner core of the fiber over a period of time. A high magnification camera may not see some of these contaminants that might not be effecting the operation of the fiber at this time but could in the future. A lower magnification camera would be able to see a might bigger picture of the whole fiber end face then the higher magnification.
With regards to multimode fiber, a low magnification gives you a good view of the end face under inspection. The benefit of using a high magnification camera on a multimode fiber is to see if there are small (in the range of 1 m) scratches or damage to the core.