Splicing optical fibers is a common task in building and repairing fiber optic networks. It helps connect two fiber cables to make one continuous link. But what if the two fibers have different core sizes? Can you still splice them together using fiber fusion splicer?
The short answer is yes, but there are some important things to know. The type of fibers you are working with matters a lot. In general, there are two main situations:
- A. Splicing Between Single-Mode and Multimode Fibers
- B. Splicing Between Same-Mode Fibers with Different Core Sizes
Each case has its own challenges and solutions, which we’ll explain below.
Understanding Fiber Core Types
Optical fibers have a center part called the core, where light travels. The size of this core and the way light moves inside it affect how the fiber works.
Single-mode fiber (SMF) has a very thin core, about 8 to 10 microns wide. It carries only one path of light and is used for long distances, like connecting cities or large buildings.
Multimode fiber (MMF) has a wider core, usually 50 or 62.5 microns wide. It carries several light paths and is used for short distances, like inside offices or data centers.
If you try to splice fibers with different core sizes or types, light may not flow smoothly, which can cause signal loss or poor performance.
A. Splicing Between Single-Mode and Multimode Fibers
Using fiber fusion splicer to Splicing a single-mode fiber to a multimode fiber is not recommended, but sometimes it has to be done. The problem is that these fibers work in very different ways. Single-mode fiber sends light in one straight path, while multimode fiber sends light in many paths. Also, the core sizes are very different. This causes several problems.
Challenges
First, a lot of the light may get lost at the point where the fibers are joined. This is called insertion loss, and it can make the signal weak.
Second, some light may bounce back toward the source, which is called back reflection, and this can damage the equipment.
Finally, the mismatch can lead to unstable or poor-quality signals.
Recommended Solutions
To solve this problem, the best option is to avoid direct fusion splicing between single-mode and multimode fibers. However, Baudcom also uses a high-precision Fiber Optic Fusion Splicer to test single-mode and multimode fusion splices, and the optical fiber splice loss is about 0.03 dB. For cases where the accuracy requirements are not so high, you can try to use direct fusion splicing.
Test video: Single mode and multimde fiber splicing
Instead, what is great is that you can use a mode conditioning patch cord. This is a special type of cable that allows the signal from a single-mode fiber to enter a multimode fiber in a more controlled way.
- Connect the single-mode transmitter or device to the single-mode end of the patch cord.
- Connect the multimode end to the multimode fiber system (for example, a patch panel or media converter).
- Make sure to follow proper polarity—MCPs are directional, and one end must be at the source
Another option is to use a media converter or optical transceiver, which can convert the signal between different fiber types electronically. If you must connect the two fiber types, it’s better to do it using connectors and patch panels instead of directly splicing the fibers. This makes it easier to control the connection and reduce signal loss.
B. Splicing Same-Mode Fibers with Different Core Sizes
Sometimes you may need to splice two fibers that are both single-mode or both multimode, but their core sizes are a little different. This is common when you’re connecting older fiber cables with newer ones.
For example, some older multimode fibers have a 62.5-micron core, while newer ones may have a 50-micron core. The same can happen with single-mode fibers that have slightly different mode field diameters.
Challenges
The good news is that splicing these types of fibers is usually possible, but it needs to be done carefully. The main issue is that the light may not transfer efficiently from one fiber to the other. If the light goes from a larger core to a smaller one, some of it might not enter the second fiber at all. If it goes from a smaller core to a larger one, the light can spread too much, causing optical fiber splice loss. This loss is not as bad as in the case of single-mode to multimode splicing, but it can still affect performance.
Recommended Solutions
core alignment fusion splicer close up
To reduce this loss, you should use a high-quality fusion splicer with core alignment technology. These splicers can adjust the position of the fibers automatically to make the connection as accurate as possible. You can also fine-tune the splicing settings, like arc power and duration, to match the fibers better.
If possible, it’s always best to use the same type and size of fiber to avoid these issues in the first place.
After splicing, always test the link using tools like an OTDR (Optical Time Domain Reflectometer) or a power meter to make sure the connection works well.
Tips That Apply to Both Cases
No matter what kind of fibers you are splicing, there are some general tips that always help.
First, always test the splice after you finish it. Use tools to measure how much optical fiber splice loss and check for any problems.
Second, label the splice point clearly, especially if you are connecting different types of fibers. This helps technicians in the future understand what was done.
Third, if possible, use connectors instead of permanent splices when joining different core sizes or fiber types. This makes the network easier to manage and upgrade later. Finally, plan your fiber network ahead of time to avoid mismatched splicing situations whenever you can.
Conclusion
It is possible to splice two optical fibers with different core sizes by fiber fusion splicer, but you need to be careful. If you are splicing single-mode fiber to multimode fiber, avoid direct splicing where precision is required. Use mode conditioning patch cords, media converters, or patch panels to make a better connection. If you are splicing two fibers with the same mode but different core sizes, you can use fiber fusion splicer with careful alignment and settings. Always test the connection and use the best equipment available to reduce signal loss. Following the right method ensures your network stays reliable and performs well.
