Single-mode fiber (SMF) is typically more expensive than multi-mode fiber (MMF). The cost difference between the two primarily stems from the different technologies and capabilities they offer.

Here are some reasons why SMF is often more expensive:

1. Technology and Construction: Single-mode fiber has a smaller core size compared to multi-mode fiber. This requires more precise manufacturing techniques, which can increase production costs.

2. Performance: Single-mode fiber offers higher bandwidth and longer transmission distances than multi-mode fiber. The enhanced performance contributes to the higher cost.

3. Equipment: The transceivers and other networking equipment designed for single-mode fiber are often more expensive than those for multi-mode fiber. This can impact the overall cost of deploying a single-mode fiber network.

4. Installation and Maintenance: Installing and maintaining single-mode fiber infrastructure may require more specialized tools and skills, adding to the overall cost.

While single-mode fiber is generally more expensive, it is also capable of supporting longer distances and higher data rates, making it suitable for applications that demand high performance over extended ranges. Multi-mode fiber is more cost-effective for shorter-distance and lower-bandwidth applications.

The specific cost difference can vary based on factors such as the quality of the fiber, the length of the installation, and market conditions.