Types of Single Mode Fibers

Types of Single Mode Optical Fiber

   We’ve already discussed how single-mode fiber is used for essentially all long-reach fiber applications.But there are also several different types of SMF.

The most common types are:
• “Standard” SMF (ITU-T G.652) A.K.A. SMF-28
• Low Water Peak Fiber (ITU-T G.652.C/D)
• Dispersion Shifted Fiber (ITU-T G.653)
• Low-Loss Fiber (ITU-T G.654)
• Non-Zero Dispersion Shifted Fiber (ITU-T G.655)
• Bend Insensitive Fiber (ITU-T G.657)

these are the different fibers defined theoretically, however the below mentioned fibers are the one you see often in the field

“Standard” Single-Mode Fiber (G.652)  

 The original and mode widely deployed fiber is Frequently called “SMF-28” or SMF. SMF-28 is actually a product name from Corning.this fiber is Optimized for the 1310/1550nm band.the Lowest rate of dispersion occurs in this 1310 band but Attenuation is lower at 1550nm, but more dispersion there.
 

Low Water Peak Fiber (G.652.C/D)

   Modified G.652 is designed to reduce water peak.Water peak is a high rate of attenuation at certain frequencies due to OH- hydroxyl molecule within the fiber.these type of fiber give very good raman gain.

Dispersion Shifted Fiber (ITU-T G.653)

    This type of fiber is a n attempt to improve dispersion at 1550nm.The rate at which chromatic dispersion occurs changes across different frequencies of light.The natural point of zero dispersion occurs at 1300nm.But this is not the point of lowest attenuation. DSF shifts the point of zero dispersion to 1550nm.But this turned out to cause big problems.Running DWDM over DSF causes non-linear interactions.The notable example is called Four Wave Mixing where 3 equally spaced wavelengths interact to produce a 4th wavelength.As a result, this fiber is rarely used today.
This type of fiber is hugely deployed in Japan.

Non-Zero Dispersion Shifted Fiber

    They have similar concept to Dispersion Shifted Fiber but the zero point is moved outside of the 1550nm band. This leaves a small amount of dispersion, but avoids the non-linear cross-channel interactions cause by DSF. To manage dispersion, NZDSF comes in 2 types, they are NZD+ and NZD-, with opposite dispersion “slopes”.One spreads the 1550nm band out and the other compresses it in the opposite direction.By switching between the two slopes, the original signal can be maintained even over extremely long distances.this is what is done in subsea cable

Other Single-Mode Fiber Types

the other type of single mode fibers are 

ELEAF, TWRS, TWS, Teralight etc

 

Dispersion of different Fiber types