What are Type of Fiber Attenuator?

2022-05-20

People often wonder why they are deliberately setting attenuation on a fiber network when they see fiber attenuators. Attenuation is one of the key points you look for when testing fiber. You want the attenuation to be as low as possible so that you can accommodate the link budget you are trying to meet or beat.

For those who don't know, attenuation refers to the amount of light or signal loss across a span or connection. When customers build a network, they always want to cover as far as possible. Sometimes fiber amplifiers are installed to increase the signal to ensure that it reaches the fiber in operation, so that the signal can reach every customer or place where it is needed. Sometimes amplifiers are added. will result in a higher powered laser, conversely, if the signal is only a short distance from your first location, it will result in the optical signal being too strong by the time it reaches the optical receiver.

It can distort the signal or burn out the optical receiver. This is where attenuators that purposely increase losses are useful and necessary. There are many types of attenuators with different levels of attenuation so that the network can be perfectly balanced. Let's take a deep dive into the different types of fiber attenuators to give you a better understanding of the different methods that help create loss and potentially save equipment costs.

1. Male and female optical attenuators
The most common optical attenuators I usually sell are male-to-female attenuators. These attenuators are used at the end of the wiring and are usually plugged into the receiving end of the transmission. Some people call them inline attenuators because they plug directly into the switch and then into the jumper. They increase at a rate of 1 dB, with attenuation levels ranging from 1 dB to 25 dB. They are available in the four most common types of fiber optic connectors, including UPC and APC polished.

Often, the best attenuation level for the application is not known. Most customers will buy on a 1 to 10 dB scale. At work, the amount of decay required is different, so they have various decays, and it becomes a "try until it works" process. Meaning, if it's 5dB at first, but it's too big and the signal is turned off, you'll know you need less attenuation and your next level will try 4dB. Repeat this process until the desired attenuation is achieved.

2. Female to female optical attenuator
There are attenuators that allow you to plug two male connectors into each other. These are bulkhead type female to female attenuators. They usually have specific wavelengths. The attenuation at the specified wavelength is only known at 1310nm or 1550nm.

This style uses wavelength-sensitive neutral density filters to help achieve the proper level of attenuation. When using this type, they only have four different dB levels. In units of 5, in units of 5 10 15 or 20dB. Use this style when you know exactly the dB level you need to attenuate and the wavelength you need to attenuate.

3. Variable Optical Attenuator
In addition to getting several attenuators with different decibel levels, there are a few other types of attenuators that allow you to change the amount of loss. One is called a variable optical attenuator. It has a mechanism mounted in the middle of the jumper, and you can turn a screw to change the attenuation. It ranges from 1dB to 20dB and operates at 1310nm and 1550nm wavelengths. It has a specific connector on each end. By turning the nut on the device, it helps to separate the connectors or helps to pull them back together. This will change the amount of loss in the system, as the end faces of the connector must touch to eliminate the loss.

Another type is the air gap attenuator. These are only available for ST and FC type connectors. This fiber, which uses its name, places different levels of space air between a pair of mated fiber optic connectors. Air attenuators involve the use of "gaskets" to induce attenuation by creating a distance between the end faces. Washing machines come in different thicknesses to help vary the amount of loss. There is no specific decibel level for this gasketed attenuator, as there are other factors that affect the amount of loss at this point. They do come in different colors to help you understand which one you tried during testing. Unlike male and female attenuators, spacers are placed on the light source or transmitter, not the receiver.


4. Passive Optical Attenuator
Another form of attenuator is called a passive attenuator. This is where you use your equipment to help attenuate patch lines that are already in place. For this type, we have two different options. One is the Clip On attenuator, which can be used on a 3mm jacketed fiber with attenuation ranging from 0 dB to 47 dB at 1550 nm. For a wavelength of 1310nm, the level is 0 to 21 dB.

When a Clip On attenuator is placed on a fiber, it bends the fiber to create the desired loss. The device can be reused, and once removed, does not affect the performance of the fiber. Another one that falls into this category is the three-stage attenuator. This only works at 1310nm wavelength. There are 3 different ranges, 2-7dB, 5-15dB and 5-20dB. The device works by exceeding the recommended fiber bend radius without introducing any back reflections.

As you can see, attenuators play a very important role in some networks. They may sound counterproductive because when you run, you're looking for minimal losses. Attenuators not only cause loss, but they can affect the signal and cause data loss on links in a network where too much light passes through. Interestingly, a component that costs about $12 can have a huge impact on a higher-cost network.

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