The **G.652, G.653, and G.655** are ITU-T standards for single-mode optical fibers

 The **G.652, G.653, and G.655** are ITU-T standards for single-mode optical fibers, each designed for different applications in fiber-optic communications. Below is a comparison of their key characteristics:


### **1. G.652 (Standard Single-Mode Fiber - SSMF)**

- **Dispersion**:  

  - Zero-dispersion wavelength at **1310 nm**.  

  - High chromatic dispersion (~17 ps/nm·km) at **1550 nm**.  

- **Applications**:  

  - Commonly used in **metro, access, and short-haul networks**.  

  - Works well for **CWDM (Coarse WDM)** and **10G/40G Ethernet**.  

- **Subcategories**:  

  - **G.652.D**: Low-water-peak fiber (enhanced for full spectrum use).  


### **2. G.653 (Dispersion-Shifted Fiber - DSF)**

- **Dispersion**:  

  - Zero-dispersion shifted to **1550 nm** (minimizing dispersion at this wavelength).  

- **Issue**:  

  - **Nonlinear effects (Four-Wave Mixing - FWM)** make it unsuitable for **DWDM** systems.  

- **Applications**:  

  - Mostly obsolete today; was used in **long-haul single-channel systems**.  


### **3. G.655 (Non-Zero Dispersion-Shifted Fiber - NZDSF)**

- **Dispersion**:  

  - Small but **non-zero dispersion** at **1550 nm** (~4–6 ps/nm·km).  

  - Optimized to **reduce nonlinear effects** (FWM, XPM) in **DWDM** systems.  

- **Applications**:  

  - Used in **long-haul and ultra-long-haul DWDM networks**.  

  - Supports **high-speed transmission (100G, 400G, etc.)**.  

- **Subcategories**:  

  - **G.655.E**: Enhanced for better performance in **C & L bands**.  


### **Comparison Summary**

| Feature          | G.652 (SSMF)       | G.653 (DSF)        | G.655 (NZDSF)      |

|------------------|-------------------|-------------------|-------------------|

| **Zero Dispersion** | 1310 nm          | 1550 nm           | ~1550 nm (non-zero) |

| **Dispersion at 1550 nm** | High (~17 ps/nm·km) | Near zero        | Low (~4–6 ps/nm·km) |

| **Nonlinear Effects** | Moderate       | Severe (FWM issues) | Minimized        |

| **Best Use Case** | Metro, CWDM, 10G/40G | Obsolete (old long-haul) | DWDM, 100G+ |


### **Conclusion**

- **G.652** is the most widely deployed fiber for general-purpose use.  

- **G.653** is outdated due to DWDM incompatibility.  

- **G.655** is preferred for **high-capacity DWDM systems** (e.g., submarine cables, long-haul networks).  


Would you like details on newer fibers like **G.656 (Wideband NZDSF)** or **G.657 (Bend-Insensitive Fiber)**?

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