Optical splitters are vital components in fiber optic networks, distributing signals from a single input fiber to multiple output fibers. However, like any other network component, optical splitters can experience loss, which impacts the overall performance of the network. Although both optical splitters and patch cords are tested using an optical power meter and light source, there are some differences in testing them.

What are Optical Splitters?

The fiber optic splitter is a device used in fiber optic networks to divide a single optical signal into multiple signals or combine multiple signals into a single one. It is a crucial component in Passive Optical Networks (PON) and is widely used in telecommunications, CATV (Cable TV), and FTTH (Fiber to the Home) applications.

Optical splitters include FBT (fused biconical) couplers and PLC (planar lightwave circuit) splitters, are common passive devices that can divide fiber light into multiple parts in a specific ratio. For example, a splitter with a 1×2 ratio configuration has one input and two outputs. Similarly, there are 1×4 splitters, 1×8 splitters, 1×16 splitters, 1×32 splitters, and so on. If a splitter has two inputs and four outputs, it is referred to as a 2×4 splitter. Optical splitters are crucial in FTTH (fiber to the home) networks as they enable multiple customers to share a single PON network interface.

Optical splitter loss refers to the decrease in optical power that happens when a single optical signal is split among multiple output ports in a fiber optic network. The signal loss in the system is measured in decibels (dB). Below is a table showing the typical losses for different types of splitters.

Excess loss is the difference between the optical power sent into the splitter’s input and the total optical power measured from all output ports. It ensures that the total output power is always less than the input.

Insertion loss is the difference between the optical power sent into a specific input port of the splitter and the optical power from any single output port. This loss includes both the splitting loss and the excess loss.

How to Test the Loss of Optical Splitter?

Before discussing the specifics of testing splitter loss, it’s important to understand a key fact. The signal attenuation in an optical splitter is symmetrical, meaning it is the same in both directions. Whether the splitter is combining signals upstream or dividing signals downstream, it introduces the same level of attenuation to the optical input signal. Therefore, the principle of testing optical splitter loss is to follow the same directions for a double-ended loss test.

Now, let’s test a basic 1×2 optical splitter, as shown in the picture below. Start by connecting a launch reference cable to the optical light source with the correct wavelength (since some splitters depend on the wavelength). Then, use the optical power meter to calibrate the output of the launch reference cable, setting the 0dB reference point. Next, connect the light source to the splitter and attach a receive launch reference cable to the output and the optical power meter. Finally, measure the loss.

Similarly, to measure the loss on the second port, move the receive launch cable to the other port and read the loss from the meter. To test the loss in the opposite direction from all output ports, simply reverse the test direction.

For other 1xN optical splitters, like a 1×32 splitter, this testing method can also be applied. Simply connect the light source to the input and use the power meter and reference cable to test each output port one by one. However, for upstream testing, you’ll need to move the light source 32 times and record the results from each output port.

Now, what about testing a 2×2 splitter? In this case, there’s a lot of data to gather, but testing is still necessary. You would need to test from one input port to both outputs, then from the other input port to each of the two outputs. The same method can be applied to test other 2xN splitters.

Tips: The loss you are measuring includes the splitter’s loss due to the split ratio, excess loss from the manufacturing process, and the input and output connectors. So, the loss you measure is what you can expect when the splitter is connected to a cable plant. Once installed, the splitter becomes one source of loss in the cable plant, and it’s tested as part of the overall cable plant loss during insertion loss testing.

Common Issues and Troubleshooting

When testing optical splitters, several common issues can arise that may affect the accuracy of your results. Understanding these issues and knowing how to troubleshoot them is essential to ensuring your fiber optic network performs optimally. Below, we will discuss some of the most frequent problems encountered during testing, along with practical tips for troubleshooting.

Common Issues During Testing

High Loss Readings: One of the most common issues is unexpectedly high loss readings. This can be caused by poor connector cleanliness, fiber misalignment, or damaged splitters. High loss indicates that more optical power is being absorbed or scattered within the splitter than expected, which can degrade the performance of the entire network.

Unstable Readings: If your readings fluctuate significantly, this can indicate an unstable connection or poor contact between the fiber and the test equipment. Other potential causes include environmental factors such as temperature fluctuations or vibrations during testing.

Inconsistent Results: Inconsistent results across different tests may suggest issues with the test setup, such as varying connector quality or improper handling of the fibers. It could also indicate that the splitter itself is faulty or that there is a problem with the calibration of the testing equipment.

Troubleshooting Tips

Clean Connectors Thoroughly: Dirty connectors are a leading cause of high loss readings. Always clean connectors before testing using appropriate cleaning tools and solutions. Even tiny particles of dust can cause significant loss.

Check Fiber Alignment: Ensure that the fiber is properly aligned with the input and output ports of the splitter. Misalignment can lead to high loss and unstable readings. Use precision tools to align the fibers correctly.

Inspect for Physical Damage: Carefully inspect the optical splitter and connectors for any physical damage. Cracks, chips, or bends in the fiber can cause high loss. Replace any damaged components before retesting.

Stabilize the Environment: Conduct tests in a stable environment, free from vibrations, temperature changes, and other environmental factors that could affect the readings. Using a controlled environment helps ensure consistent results.

Verify Equipment Calibration: Regularly calibrate your optical power meter and light source to ensure they provide accurate readings. Inconsistent or incorrect calibration can lead to unreliable results.

Best Practices for Accurate Results

Use Quality Components: Ensure that all connectors, fibers, and splitters used in the testing process are of high quality and free from defects.

Document Results: Keep detailed records of each test, including the equipment used, environmental conditions, and specific readings. This helps in identifying patterns or recurring issues.

Repeat Tests: Conduct multiple tests to confirm the consistency of the results. This can help in identifying any anomalies that may have occurred due to temporary issues.

By addressing these common issues and following the troubleshooting tips provided, you can enhance the accuracy and reliability of your optical splitter loss tests, ensuring that your fiber optic network performs at its best.

Why is Testing Optical Splitter Loss Important?

Testing optical splitter loss is crucial for several reasons:

Ensuring Adequate Signal Strength: High splitter losses can result in reduced signal strength at the output ports, leading to degraded performance and potential data transmission errors. By regularly testing loss, you can identify and address issues that may compromise signal quality.

Optimizing Network Performance: Understanding the loss characteristics of optical splitters allows you to optimize network design and configuration. You can make informed decisions about splitter placement, cable routing, and amplification requirements to maximize overall network efficiency.

Preventing System Failures: Excessive splitter loss can contribute to system failures or performance degradation. Regular testing helps identify potential problems before they escalate, preventing downtime and costly repairs.

Compliance with Standards: Many industries and regulatory bodies have specific requirements for optical splitter loss. Testing ensures that your equipment meets these standards and avoids compliance issues.

Troubleshooting Network Problems: If you’re experiencing network performance problems, testing optical splitter loss can help isolate the root cause. By identifying excessive loss, you can take corrective measures to restore proper functionality.

Conclusion

Optical splitters are very important passive optical components used in PON architecture. Holight provides high-quality optical splitters and test tools such as optical power meters, light sources, and more.