Introduction of Fiber Optic Attenuators

Do you know what is the fiber attenuator used for? As we know, the source of the single mode fiber is laser, the power of which is extremely strong. Therefore we can use single mode fiber to achieve long distance transmission. But, if the transmission distance over single mode fiber is too short, too much light may overload a fiber optic receiver, which may cause serious high bit error rates. How to solve this? Fiber attenuator should be inserted at the receiver end to reduce the power to the proper level. This article sheds light on types, and applications of optical attenuators, helping you to choose a right one.

What is Fiber Attenuator?
Fiber optic attenuator is a passive device used to reduce the power level of an optical signal because too much light can overload a fiber optic receiver and degrade the bit error ratio (BER). To achieve the best BER, the light power must be reduced by using fiber optic attenuator. Generally, the optical attenuators are used in single-mode long-haul applications to prevent optical overload at the receiver.

Optical attenuator reduces signal power by absorbing the light, like sunglasses absorb the extra light energy. Or by scattering the light like an air gap. Fiber optic attenuators are commonly used in two scenarios:

1.Attenuators are permanently installed in a fiber optic links to properly match signal levels at transmitter and receiver.
2.In fiber optic power level testing. Attenuators are used to temporarily add a calibrated amount of signal loss in order to test the power level margins in a fiber optic system.

Types of Fiber Optic Attenuators

Optical attenuator takes a number of different forms. They are typically grouped as fixed optical attenuator and optical variable attenuator.


What is Fixed Fiber Attenuator?
Fixed fiber optic attenuator, also called fixed plug type or fixed build-out fiber attenuator, is used in fiber optic communications to reduce the optical fiber power by a certain level. Typical attenuation values are between 1 and 30 dB. Usually, it has a male plug connector at one side to allow fiber attenuator to be plugged directly into receiver equipment or adapters in patch panel, and has female type fiber optic adapter at the other side to allow the patch cords to plug in. Fixed fiber optic attenuator name is based on the connector type and the attenuation level. LC attenuator 5dB means this attenuator uses LC fiber optic connector, and it can reduce the optical fiber power level by 5dB.

What is optical variable attenuator?
Optical variable attenuator can also be made as a plug-in card. It is a part of Fiber-Mart, all-in-one multi-service transport system. This hot-swappable plug-in variable optical attenuator is an online attenuation adjustment device, only occupying one slot in the 1U/2U/4U chassis. It is applied to applications that optical power required strict control, such as to balance signal strengths in a DWDM network system. Card optical variable attenuator adopts MEMS technology and could continually and variably reduce the light intensity in the optical network and help simulate distance or actual attenuation in the fiber optic testing work. With the card design, this optical variable attenuator is easy to install and remove without any tool. The online attenuation adjustment also contributes to safer business.


How to use Fiber Optic Attenuators in data link?

For a single-mode applications, especially analog CATV systems, the most important parameter, after the correct loss value, is return loss or reflectance. Many types of attenuators (especially gap loss types) suffer from high reflectance, so they can adversely affect transmitters just like highly reflective connectors.


Fiber Optic Attenuator in Data Link

Choose an attenuator with good reflectance specifications, and always install the attenuator ( X in the drawing) at the receiver end of the link as shown above. This is because it’s more convenient to test the receiver power before and after attenuation or while adjusting it with your power meter at the receiver, plus any reflectance will be attenuated on its path back to the source.

Test the system power with the transmitter turned on and the optical attenuator installed at the receiver, and using an optical power meter set to the system operating wavelength. Check to see whether the power is within the specified range for the receiver.

Fiber optic attenuator is an essential passive component in the optical communication system. With the advancement of DWDM technology, as well as the potential to flexibly upgrade the reconfigurable optical add-drop multiplexer (ROADM), the demand for optical attenuator is sure to soar, especially for optical variable attenuator. The innovation in fiber optic industry never ceases, and fiber optic attenuator will evolve to have lower cost, faster response time and enhanced integration of hybrid with other optical communication devices.Fiber-Mart provides a wide range of fiber optical attenuator.Welcome to contact with


What does an Optical Attenuator do ?

With the advancement of DWDM technology, as well as the potential to flexibly upgrade the reconfigurable optical add-drop multiplexer (ROADM), the demand for optical attenuator is sure to soar, especially for optical variable attenuator.


Optical Attenuators, or fiber optic attenuators, are used in optical communications to reduce optical fiber power at a certain level. Generally, the attenuator types are classified by connector types and attenuation levels. A common version is the female to male plug type bulkhead attenuator which has a connector at one side and a adapter at the other fiber optics, attenuation can also be called transmission loss. It’s the reduction in light signal intensity with regards to the distance traveled by the signal inside a transmission medium. Attenuation is an important element to limit the transmission of the digital signal driving considerable distances. Optical attenuator reduces this optical signal because it travels along a totally unoccupied space or perhaps an optical fiber.


Optical fiber attenuators may employ several principles when utilized in fiber optic communications. One common principle may be the gap loss principle. Attenuators by using this principle are responsive to the modal distribution ahead of the attenuator. Thus, they should be utilized at or close to the transmitting end. Otherwise, the attenuators could establish less loss than intended. This problem is avoided by attenuators which use absorptive or reflective principles

Types of Fiber Optic Attenuators:

Optical attenuator takes a number of different forms. They are typically grouped as fixed optical attenuator and optical variable attenuator

The fixed attenuator, as the name implies, has a fixed attenuation level. Fixed attenuator can theoretically be designed to provide any amount of attenuation that is desired and be set to deliver a precise power output. Fixed attenuators are typically used for single-mode applications. They mate to regular connectors of the identical type for example FC, ST, SC and LC.

variable optical attenuators (VOA) resistors are replaced with solid state devices like the metal semiconductor field effect transistor (MESFETs) and PIN diodes. VOA attenuates light signal or beam inside a guarded manner. Thus producing an output optical beam with various attenuated intensity. The attenuator adjusts the ability ratio between your bright beam from the tool and the light beam entering the device over a changeable rate. VOA is usually used in fiber optic communication systems to manage optical power levels in order to prevent damages in optical receivers which may be due to irregular or fluctuating power levels. Price of commercial VOA varies depending on the manufacturing technology used.

Working Principle of Optical Attenuator

Optical attenuator usually works by absorbing the light, like sunglasses absorb the extra light energy. It typically has a working wavelength range in which it can absorb the light energy equally. It should not reflect the light since that could cause unwanted back reflection in the fiber system. Another type of attenuator utilizes a length of high-loss optical fiber, that operates upon its input optical signal power level in such a way that its output signal power level is less than the input level. The power reduction is done by such means as absorption, reflection, diffusion, scattering, deflection, diffraction, and dispersion, etc.


Applications of Optical attenuators 

A set optical attenuator fixed amount of attenuation of the optical road to the sunshine energy is principally used for its excellent temperature characteristics. Within the commissioning from the system, widely used in analog optical signal through the corresponding period of optical fiber attenuation or reduce the margin from the optical power the relay station may also be used to prevent saturation from the optical receiver; optical test instrument calibration scaling. For different line interface, you can use different fixed attenuator; if the interface is really a pigtail type available pigtail type optical attenuator welded towards the optical path between the two sections of fiber; If you are debugging the machine connector interface converter or inverter-type fixed attenuator.

Fiber optic attenuator is an essential passive component in the optical communication system. In practical applications often require attenuation quantity of the optical attenuator could be changed using the user needs. Fiber-Mart provides optical attenuators with various connector types, such as FC/SC/ST/LC/E2000, available with APC or UPC polish. Our fixed attenuators can be with different attenuation levels from 1 dB to 30 dB (step by 1 dB), while the variable optical attenuators (generally used as in-line attenuators) can be with a range of 0 ~ 60 dB. Customers can buy these attenuators directly in this category or Make Customized Orders. Any question pls feel free to contact us. E-mail:


How to use an optical attenuator to test the sensitivity of a fiber optic transceiver?

Do you know how to use an optical attenuator to test the sensitivity of a fiber optic transceiver?In order to maximize the performance of our fiber optic transceivers, welcome to join our Fiber-Mart editors to see how to learn this skill. When the optical input power is within a certain range, the optical fiber receiver has the best performance. But how can we determine if the fiber optic transceiver will provide the best performance at the lowest optical input power? One commonly used method is to use an optical attenuator such as a diaphragm attenuator. Usually only two values are needed to complete the test. The process includes the following three steps.


1.Use a power meter to measure the optical output power of the fiber optic transmitter. Remember that industry standards define the optical input power of transmitters and receivers for specific network standards. If you are testing a 100BASE-FX transceiver,use a 100BASE-FX transmitter and the transmitter’s optical output power should be within the manufacturer’s data sheet.

2.Connect the transmitter to the receiver and verify it is operating at the maximum optical output power available from the transmitter. You need to test the receiver with the minimum optical input power that the receiver can accept, while the receiver still provides the best performance. To do this, you need to obtain the lowest light input power value from the manufacturer’s data sheet.


3.Calculate the level of attenuation required for the test. For example, the transmitter’s optical output power is -17 dBm, and the receiver’s minimum optical power level is -33 dBm. The difference between them is 16 dB. You can use a 16 dB bulkhead attenuator at the input of the receiver and retest the receiver. If the receiver still works, it is within specification.

Note: Light loss is not considered in the above example. Assuming the transmitter is located 10 kilometers from the receiver and the loss of the entire fiber link (including the interconnect) is 6 dB, then a 10 dB bulkhead attenuator should be used instead of 16 dB for your test.


The optical attenuator is a very important passive optical fiber device. It can attenuate the optical signal energy according to the user’s requirements. It can also be used to test the sensitivity of optical fiber transceivers. Fiber-Mart offers a full range of optical attenuators that bring convenience to users of optical communications.Any questions welcome to communicate with us: