English
Deutsch
Espaniol
Optical fibers are an excellent medium for the transmission of light signals and rarely require amplification compared to copper cables. High-quality single-mode optical fibers (SMF) in industrial quality generally operate with a very low attenuation of around 0.1 dB per kilometer.
The strength or power of the optical signal (measured in dB or decibels) will always be higher at the network operator's central office than at the customer's premises. Signal loss over a fiber optic link is unavoidable as the signal degrades over the length of the link. Operating a fiber optic link or any other type of network connection with significant insertion loss is not desirable as it can negatively impact the overall performance of the network. Therefore, understanding, measuring and mitigating insertion and other errors is critical to network deployment and testing.
For network engineers and planners, most of the loss budget is accounted for by the link between the end node and the consumer's network connection. Splitters add significant losses to any fiber network - far more than passive components such as fiber connectors. When we measure and calculate the attenuation effects of various optical components, we use the terms return loss and insertion loss.
Insertion loss and its causes
Simply put, insertion loss (IL) is the measurement of the signal (in the form of light) that is lost over a fiber optic link. Insertion loss is an inherent part of fiber optic systems; we measure it in decibels and should always be a positive number. In addition, a lower insertion loss value reflects a better condition of the link. For example, an insertion loss (IL) of 0.1 dB is better than 0.3 dB. Although we consider this type of loss to be intrinsic to fiber optic cable, some problems can arise from these losses. Also, there are some practices we can use to prevent excessive losses. Let's talk more about this topic. Here are some common causes of high insertion loss;
Environmental factors:
Sometimes environmental factors such as humidity and temperature can also affect the performance of fiber optic cables and lead to excessive insertion losses. Therefore, the atmosphere of the network should be controlled and monitored.
When connecting two optical fibers with different core sizes, numerical apertures or modes, a mismatch may occur at the connection point. This mismatch can lead to a considerable loss of signal power, as some of the light has to be coupled from one fiber to the other.
Dirty connectors: Dirt, dust or other contaminants on the surfaces of the connector sleeves can obstruct the flow of light and lead to signal loss. Through thorough preventive maintenance and regular cleaning, we can ensure that insertion loss in connectors is minimized.
Bending and micro-bending:
Bends are a common cause of insertion loss because when fibers are twisted or bent, some of the transmitted light tends to escape the core due to macrobends or microbends. This type of loss often occurs in installations where fiber optic cables are routed through conduits with steep bend angles. Bend resistant fiber optic cables are an excellent option for installations with too many bends.
Fiber quality and production:
With inferior fibers, the construction of the cladding and core is not uniform, resulting in higher insertion loss. Therefore, it is always advisable to use higher quality fiber optic cables that are manufactured using high quality and precise manufacturing processes.
Wavelength mismatch:
High insertion loss due to wavelength mismatch is a problem that occurs when we use a combination of unsuitable light sources and fibers. Higher scattering or absorption can lead to higher insertion losses in such cases.
Choose quality cables and equipment.
How can higher insertion loss be avoided?
In the following part of the article, we will discuss some practical solutions for avoiding higher insertion loss.
Invest in high-quality equipment:
Many network operators use low-cost network components and cables! Investing in high quality components pays off in many ways, and low insertion loss is one of them. High quality components are more expensive but are manufactured under stricter quality controls and in accordance with various standards.
Inspection and cleaning of plugs:
Each connector manufacturer suggests different maintenance schedules for their different types of connectors. In general, as prescribed by the manufacturer, regular inspection and cleaning of the connectors is required to remove deposits such as dirt and dust on the connector sleeves. We already know that such deposits can obstruct the flow of light and lead to signal loss.
Compatibility of the connections:
With so many options available, it is important to use compatible connectors in terms of mode type, numerical aperture and core size. Mismatched connectors work well but can result in higher insertion loss.
Careful management of the cable:
During installation, you must avoid excessive twisting or bending of fiber optic cables. Avoiding micro and macro bends is also important to keep insertion loss across a connection within appropriate limits. Always use the correct tools and techniques when working with cables. Only use bend-insensitive fiber optic cable if you cannot avoid many steep bends and twists in your cabling plans.
Maintain optimum bending radii:
Maintaining an optimal bend radius during and after the installation of fiber optic cables is critical as it has a significant impact on insertion loss. The best way to achieve a solid installation with an optimal bend radius is to fully comply with the cable manufacturer's recommendations. According to the Fiber Organization, the typical long-term minimum bend radius should be ten times greater than the cable diameter. However, consumers should always consult with the cable manufacturer for the best results.
Prevent wavelength mismatch:
Select LEDs or lasers that emit light at a wavelength complementary to the fiber used. Operating a fiber optic network system with mismatched wavelengths can lead to excessive insertion losses and other interference.
Precision splicing and splitting:
Improper or poorly executed splicing is often associated with excessive insertion losses. Therefore, we should always use proven techniques and precision tools for splitting and splicing to create efficient connections.
Handling and storage:
Optical fibers look like other cables, but we must understand that these cables are different because they are made of fragile glass strands. Therefore, always handle fiber optic cables with care when storing them. Also, try to follow the cable manufacturer's instructions for handling and storage.
Training, qualification and certification:
Here comes another critical point! Make sure the people who handle the fiber optic cables and other components of your network are well trained and knowledgeable about best practices. Consider investing in a training program to help new hires learn and improve the skills of existing technicians.
Conclusion:
This article was about insertion loss, its most common causes and possible remedies. Insertion loss is an inherent feature of fiber optics that we cannot eliminate. However, it is possible to improve the performance of the network by limiting insertion loss through various means. In this post, we have discussed the importance of following the cable manufacturer's recommendations and choosing higher quality cables and components.
Also, it sometimes happens that the network suffers excessive insertion loss due to poor practices and maintenance. In this context, it is important to ensure that the people involved in the construction and operation of the network are well trained and have the necessary knowledge.
