Nowadays, the high-speed transfer of data around the globe depends on fibre optics, but signal loss and attenuation can cause issues. If these losses are not managed, your network may face slow speeds and reduced performance. However, stay calm! There is a good news that loss can be minimized.
Therefore, the purpose of writing this blog is to make you familiar about fibre loss problems and their causes in fibre optic cables. So, in this article, you will find what the fibre signal loss is, its types, measurement and also tips to minimze such looses. So, be with us!
Figure no 1 Fibre optic Signal loss and attenuation
1) คืออะไร Optical Fibre Loss?
“Fibre optic loss occurs when a part of the light currently travelling through the cable becomes weaker before reaching the terminal end.”
Moreover, imagine a scenario where a person is shouting deep into a tunnel; initially, the voice carries well, but as it travels more, its volume decreases. This fading is referred to as attenuation in fibre optics, where it is measured in decibels per kilometre (dB/km).
- Fibre optic loss vs Attenuation
Now, you may ask what the difference between loss and attenuation is. Well! Loss describes any drop-off in signal power. On the other hand, attenuation refers to a specific type of loss that occurs in the fibre due to light absorption and scattering. Additionally, keep in mind that this is especially important when using long-distance internet or high-speed networks.
However, in the absence of solutions, video calls would lag, streaming would buffer repeatedly, and downloads would slow significantly. This is why minimizing fibre optic loss is extremely critical.
2) Types of Fibre Optic Loss and their Causes
Optical fibre loss ( db/km ) is categorized into two groups: Intrinsic and extrinsic. These are further categorized into various types, each having a different cause. So, let’s break it down!
i) Intrinsic Losses
This type of loss refers to loss caused by the fibre material itself. Unluckily, it cannot be completely removed from the fibre, but some of it can be reduced by using high-quality material.
a. Absorption Loss
Let’s say you flash a light through a dirty window, but some light does not pass through. Similarly, in your fibre optic cables, when light enters the glass core, it absorbs energy due to the glass’s tiny impurities transforming it into heat which is known as absorption loss.
- Main cause:
- The major reason of absorption loss is the small concentrations of OH- ions (water molecules) present in your fibre. These ions capture energy which weakens the signal around 1383 nm. Keep in mind that most glass even if it is optimally pure, will absorb energy. However, some materials better suited for fibres can minimize this issue.
- Example:
At 1550 nm, a good-quality fibre has an absorption loss of roughly 0.2 dB/km. If the fibres have more impurities, the loss gets even increased.
Figure no 2 Types of Fibre loss
b. Scattering Loss
Have you ever watched fog scatter sun rays? That is what happens in your fibre optic cable. For instance; when microscopic changes in the fibre’s material cause light to scatter in varying directions, this is known as Rayleigh scattering.
- Main cause:
- The fibre’s small density changes during the manufacturing process. These small imperfections change the scattering of energy.
- Example:
- Losses due to Rayleigh scattering are 0.18 dB/km at 1550 nm and rise to 2.5 dB/km at 850nm. That’s why we prefer longer wavelengths for distance communication.
ii) Extrinsic Losses
Extrinsic loss is the opposite of intrinsic loss; it happens due to actions performed on the fibre, such as excessive bending, poor connections, and adding more network elements than needed. Don’t worry, almost all these issues can be fixed or are under your control.
c. Bending Loss
If you bend a straw beyond a certain angle, the liquid stops being able to flow freely. Similarly, if you over-bend your fibre optic cable, the same thing happens. Rather than being perfectly contained in the core, a portion of the light leaks out, which is detrimental to the signal value. Let’s see its types!
- Macrobending: Large bends in your fibre cable like when it is coiled too tightly or stood on have consequences as well. For instance, losing a lot of signals can be expected when the fibre is subjected to tighter than 30 mm radius bends.
- Microbending: This type of bending loss is the result of external pressure and bad installation of the fibre. For instance, you know a dent in the fibre can cause an increase in the loss by 0.5 dB or even more.
d. Fiber Connector and Splicing Loss
Each time you join two optical fibre cables, some amount of light loss is possible due to a lack of precise alignment. This occurs both at the connectors and the splice joints, and it can negatively impact your network. Let’s break down its types!
- Fusion splicing: This technique joins the fibres through heat, and it provides low loss connection (around 0.1 dB loss).
- Mechanical splicing: The fibres are bonded together using a glue and will approximately lose 0.5 dB or more if done improperly.
Moreover, keep in mind that if the output ends of your fibres are just aligned, even a small gap may cause a significant loss of signals.
e. Insertion Loss
Apart from all, the fibre network is losing quality due to the addition of elements such as connectors, splitters, and couplers which lowers the amount of good signal in the system.
For example, the standard connector increases loss to about 0.2 dB. Moreover, depending on the type of splitter, additional loss is set down to 3 dB and greater, meaning the signal will be halved.
Moreover a person on Qoura, Peter Brown who is a Operation Specialist at Shanghai Baudcom Communication Device Co., Ltd has also tell the same above mentioned reasons of fibre loss. So, we have to consider these and look foe solutions to enjoy high speed interent without any lagging.
- Summary Table
| Loss Type | Cause | Effect | Typical Loss |
| Absorption loss | Impurities (OH- ions) | The light turns into heat | 0.2 dB/km |
| Scattering loss | Material imperfections | Light misdirected | 0.18 dB/km |
| Macrobending loss | Large fibre bends | Light leaks out | High if <30 mm |
| Microbending loss | Tiny fibre deformations | Light misdirected | 0.2 dB/connection |
| Connector Loss | Poor alignment | Less light passes through | 0.5 dB+ |
| Splicing Loss | Bad fibre joining | Weakens data transmission | 0.1 dB (fusion), 0.5 dB (mechanical) |
| Insertion Loss | Extra components (splitters) | Signal weakens | 3 dB/splitter |
3) Measurement of Optical Attenuation
The measurement unit for losses in fibre optics is decibels per kilometre (dB/km). This indicates the level of signal strength that is lost for every kilometre of fibre optic cable the light travels through. Moreover, having a lower value in dB/km means that the fibre is clearer and maintains data better.
- Methods to assess the signal loss in the fiber:
i) Optical Time-Domain Reflectometer (OTDR ): You can consider it as a radar for your fibre. It sends pulses of light through the cable and estimates how much is reflected back. Apart from this, the OTDR can also pinpoint exact locations for weak spots, breaks or bends.
Figure no 3 Optical Time-Domain Reflectometer (OTDR )
ii) Cutback Method: This technique involves sending light through the fibre and taking measurements of residual light at the input and output ports. Such a technique is highly reliable, however, due to the need for severing the fibre, a small piece will be wasted.
Figure no 4 Cutback Method
iii) Power Meter Measurements: This method involves the use of a light source along with a power meter to measure the light present at the terminal end of the cable. This approach is straightforward and hence preferred during the initial setup and regular maintenance of fibre optic networks.
Figure no 5 Optical Power metre
Thus, by periodically checking the attenuation, you ensure that the fibre remains in optimal condition and continues to facilitate speedy data transfer.
4) Optical Fibre Loss Calculation
You can also calculate the optical fibre loss by using the below-mentioned formula;
Loss (dB)=10 × log10 (Pin /Pout )
Where:
Pin = Input power, or the signal strength at the start.
Pout = Output power, or the signal strength at the end.
In this case, the unit of measure is decibels (dB), meaning the level of signal loss.
- Example Calculation
Let’s assume your input power is 1mW and the output power is 0.5mW. The loss incurred is calculated as follows:
Loss = 10 × log10 ( 1/0.5 ) =10 × log10 ( 2 ) = 3 dB Loss
Thus, this results in a loss of 3 dB of signal power.
- Loss per Kilometre
Moreover, if you want to find attenuation per Kilometre, the you can use below mentioned formula!
Attenuation ( db/km ) = Total Loss/ Fibre length
5) Tips to Minimize Fibre Loss
In this section, I’ll share with you some useful tips which you can utilize to enjoy your internet without facing signal loss problems. So, let’s get started!
? Use Quality Fibre: As always, starting with the best materials is essential. Some of them come with tiny flaws which will absorb light and weaken the signal, like some fibre optic cables. So, go for ultra-pure silica glass, as it is refined with great care to reduce all impurities even OH-ions.
? Handle with Care: Moreover, I must say that your actions should complement the design of the optical system. Consider fibre optic cable as a very delicate piece of glass straw. Do you know that bending a straw too much leads to loss? So, we suggest avoid sharp corners and tight ties that can compress the fibre as those can create bends to the signal and ultimately weaker signals.
Figure no 6 Testing cables regularly
? Use Good Connectors And Splicing: Furthermore, keep in mind that your signal will drop if your connectors are dirty or out of alignment. Make sure you clean them before plugging in. When it comes to splicing fibres, I would suggest you to do fusion splicing (melting the ends together). This is because, using this you lose less about 0.1 dB as opposed to mechanical splicing, which has losses of 0.2-0.75 dB.
Figure no 7 Fusion splicing of fibre cables
? Test and Maintain Regularly: Lastly, perform testing even if your fibre is perfectly installed. It can be tested with an OTDR or a power meter for weak points. Moreover, regularly cleaning and inspecting your connectors will eliminate any unnecessary loss, thus keeping the network running.
6) Final Verdict
Now you are aware that fibre optic signal loss and attenuation can hinder network speed and reliability. The good news is it can be minimized. You just bring in the use of quality fibre, careful handling, good connectors, and moreover routine testing will guarantee a strong signal. Though fibre optics bring in speed and efficiency, however their true potential is enabled with the right care. Thus ensuring a smooth connection for years down the line.
Moreover, I would recommed you to buy fibre optic cables from Dekam Fibres. Our optical fibres have passed CE, ROHS, and other professional certifications. Thus, ensuring that our products are of good quality and safe. So, visit our website today!
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