There are three Single-mode Fibers used extensively in access networks:
Traditional G652.D Fiber is highly backward compatible as it has been used in all networks for many years. However, advanced cable design and installation options that require higher bend resistance may be limited by using these fibers. Higher attenuation might also limit coverage area and disallow some upgrade paths that low-loss G.652 fibers support;
Low-loss G652.D fiber is also fully backward-compatible and their lower attenuation allows for extended network coverage and extra margin to allow future upgrades, and accommodate repairs. However, lacking additional bend resilience, they are also limited to allowing cable and hardware miniaturization and low-cost deployment techniques.
Bend Insensitive G657.A & G657.B Fibers have become popular single-mode fibers in outside plant (OSP) installations in recent years as their bend resistance enables smaller cable designs and low costs installations techniques. These fibers, however, tend to be designed with smaller mode field diameter (MFD) and may feature a lower refractive index ‘trench’ region around the core to assist in bend resistance which can cause difficulties during installation