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Frequently Asked Questions

 Passive optical Components/Devices FAQ


 1. What is the passive optical device?

Optical passive device is a kind of optical device that does not require a source of energy for its

operation. Its work principle follows the optic geometry theory and optic physics theory. All the

technical data, calculation formula and test methods are associated with the fiber optics and

integrated optics.


2. How to classify the Optical Passive Devices?

Passive optical devices can be classified by the technical process and the functionality. According to

the manufacturing technical process, they can be classified as fiber passive optical devices and

integrated passive optical device. Based on their functionality, they also can be classified as optical

connector, amplifier, attenuator, power splitter, WDM devices, isolator, switch and so on.


3. What are the technical data to evaluate the passive optical devices?

 The evaluation technical data includes insertion loss, reflective loss, operation bandwidth, ripple,

wavelength passband, channel passband, channel spacing, extinction ratio, switch rate and so on. The

technical data are varied for different devices. But most passive optical devices require low insertion

loss, high reflective loss, and wide bandwidth.


4. How to evaluate the reliability of a passive optical device?

The reliability is evaluated by how the device performance changed in various environments such as in

high/low temperature, high/low temperature cycle, shock, vibration, high-temperature aging test,

humidity, and salty fog test. According to the requirement of related standards, the less change the

optical technical data has, the higher reliability the device has.


5. What is EDFA?

EDFA is Erbium Doped Fiber Amplifier, which is a kind device that began to use in the optical

transmission system since '90 and brought a revolution to the optical fiber communication technology.

The development of the EDFA is mainly based on the research for the application of 1.55um wavelength

active optical devices. The prophase research is focus on the optical fiber laser and lanthanide doped

optical fiber. Then they found that the erbium doped optical fiber can achieve optical amplification and

the operation wavelength is corresponding to the 1.55um transmission wavelength. So the EDFA is

realized based on this research fruit.


6. What is the EDFA for CATV? How is its application?

EDFA-TV Series is design to use in CATV. It is installed before the CATV transmitter to amplify the

output optical power and reallocation it to various transmission trunk line. When the trunk line is

diverged, the EDFA can be installed before the divergence as line amplifier to compensate the

divergence loss.


7. How to monitor the EDFA in the optical transmission network management system?

 As a function module in the whole system, EDFA has two ways to adopt into the network management

system. One is to transmit the performance data and alarm signals of the EDFA into the network

management system via the EDFA 232C interface, and then reach uniform management, display and

treatment. The second way is to send the switch data to the network management system via the EDFA

switch information interface. The two ways are all used in the engineering application.


8. What is EDFA Gain Module/Block Series for DWDM? How is its application?

DWDM technology is the most effective way to expand the optical communication capability today.

EDFA Gain Module/Block series for DWDM are the key components in the DWDM transmission system.

 It can effectively solve the insertion loss that caused by the mux/demux and make the relay to be easy

in the DWDM system. Due to its 40nm operation bandwidth, EDFA can amplify different optical signals

with multiply wavelengths at the same time. It can be conveniently used in DWDM system to

compensate various optical power losses.


9. What are EDFA modules? What are their advantages?

EDFA modules are integrated EDFAs, which have optic-electric integrated EDFA modules and optical

gain module. EDFA module has the features of compact size, low power loss, and easy to be used. They

can be easily installed in various application systems, such as SDH rack, CATV box, and DWDM system

rack, according to user's specific application requirements.


10. What is the difference among the single mode connector, multi-mode connector and optical data


l   The optical fiber/cable of the Single mode optical fiber/cable connectors is single mode with core

    diameter of 9um. They are used in the single mode optical fiber/cable systems.

l   The optical fiber/cable of the multi-mode optical fiber/cable connectors is multiple mode with core 

    diameter of 50um. They are used in the multi-mode optical fiber/cable systems.

l   The optical fiber/cable of the data optical fiber/cable connectors is data fiber with core diameter of

    62.5um. They are used in the data optical fiber/cable systems.


11. What is optical attenuator? What types it has?

Optical attenuator is the component used to reduce the optical power level of an optical signal. The

basic types of optical attenuators are continuously variable, step-wise variable and fixed.


12. What is the optical coupler? What are the technologies to make the optical couplers?

The optical coupler is a component to combine the optical signals in a particular couple area and then

split them again. The most often used technologies are optic components combination, Fused Biconic

Tapered (FBT), and Planar Lightwave Circuit (PLC).

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