TE and 4iG to Construct New Subsea Cable

Single-mode optical fibers are designed to carry light along a single optical mode, enabling high-speed, long-distance data transmission with minimal signal degradation. They are categorized based on their design, wavelength performance, and dispersion properties. Below are the major types of single-mode optical fibers:

1. Based on ITU-T Standards

The ITU-T has defined different types of single-mode fibers in its G.65x series, each suited for specific applications:

1.1. G.652: Standard Single-Mode Fiber (SMF)

• Description: Commonly used single-mode fiber with a zero-dispersion wavelength near 1310 nm and optimized for operation in the 1260–1625 nm range.

• Variants: G.652.A, G.652.B, G.652.C (low water peak), G.652.D (low attenuation across all bands).

• Applications: Metro, long-haul, and access networks (e.g., FTTH and GPON).

1.2. G.653: Dispersion-Shifted Fiber (DSF)

• Description: Designed to have zero dispersion around the 1550 nm wavelength.

• Advantages: Optimized for early WDM systems.

• Limitations: Susceptible to nonlinear effects like four-wave mixing (FWM) in dense WDM systems.

• Applications: Limited use in modern networks due to FWM issues.

1.3. G.654: Cut-Off Wavelength-Shifted Fiber

• Description: Optimized for ultra-long-haul and submarine optical systems with low attenuation in the 1550 nm range.

• Core Material: Typically uses large effective area to reduce nonlinear effects.

• Applications: Submarine and transoceanic communication systems.

1.4. G.655: Non-Zero Dispersion-Shifted Fiber (NZ-DSF)

• Description: Designed with small, non-zero dispersion in the 1550 nm range to minimize nonlinear effects like FWM while supporting WDM.

• Applications: Long-haul and DWDM systems.

1.5. G.656: Wideband Non-Zero Dispersion Fiber

• Description: Offers low but non-zero dispersion across a wide wavelength range (1460–1625 nm), optimized for CWDM and DWDM.

• Applications: High-capacity metro and access networks.

1.6. G.657: Bend-Insensitive Single-Mode Fiber

• Description: Designed to maintain signal integrity under tight bending conditions with minimal loss.

• Variants:

• G.657.A1 and G.657.A2 (compatible with G.652.D fibers).

• G.657.B3 (higher bend resistance for FTTH installations).

• Applications: FTTH, data centers, and premises wiring.

2. Based on Dispersion Properties

2.1. Standard Dispersion Fiber

• Description: Zero dispersion occurs near 1310 nm.

• Applications: Early single-mode fiber applications, now largely replaced by G.652 fibers.

2.2. Dispersion-Shifted Fiber (DSF)

• Description: Zero dispersion shifted to 1550 nm.

• Applications: Long-distance communication, although less common due to nonlinear effects.

2.3. Non-Zero Dispersion Fiber (NZDF)

• Description: Small but non-zero dispersion in the 1550 nm range.

• Applications: Modern DWDM systems.

3. Based on Core Design

3.1. Step-Index Single-Mode Fiber

• Description: Has a uniform refractive index in the core and a lower refractive index in the cladding.

• Applications: Standard telecommunications.

3.2. Graded-Index Single-Mode Fiber

• Description: Core refractive index gradually decreases toward the cladding, though rarely used in single-mode designs.

• Applications: Experimental or niche use cases.

4. Based on Application

4.1. Telecommunication Fiber

• Designed for long-haul and metro networks, optimized for low attenuation and high performance.

4.2. Specialty Single-Mode Fiber

• Polarization-Maintaining Fiber (PMF): Maintains polarization of light, used in sensing and laser systems.

• Erbium-Doped Fiber (EDF): Used in amplifiers for optical signal boosting.

4.3. Bend-Insensitive Fiber

• Suited for indoor use, such as FTTH and data centers, where tight bends are common.

Summary Table

S #	Fiber Type	Optimized Wavelength (nm)	Key Feature Applications
1	G.652 (Standard SMF)	1310, 1550	General-purpose, low water peak FTTH, metro, long-haul networks
2	G.653 (DSF)	1550	Zero dispersion at 1550 nm Legacy DWDM systems
3	G.654 (Cut-Off Shifted)	1550	Ultra-low attenuation Submarine and transoceanic systems
4	G.655 (NZ-DSF)	1550	Non-zero dispersion DWDM, long-haul
5	G.656 (Wideband NZDF)	1460–1625	Wide dispersion range CWDM, metro
6	G.657 (Bend-Insensitive)	1260–1625	High bend tolerance FTTH, data centers

These different types of single-mode fibers address a variety of needs, from traditional telecommunications to cutting-edge data centers and specialized applications.