Practical Knowledge About Optical Module

With the rapid development of fiber optical technology, various optical communication products are available on the market. Optical module is a small size but important optical component in telecommunication and data communication applications. Being able to realize the photoelectric conversion, it is popular among network users and vendors. To avoid unnecessary loss when using optical modules, it is necessary to master the skill of selecting patch cable for an optical module as well as installing or removing an optical module. This passage is going to guide you how to select patch cable for optical module and install or remove optical module.

Overview of Optical Modules and Patch Cables

Before we come to the practical content, let’s learn something basic about optical modules and patch cable. Optical module is a self-contained component that can both transmit and receive signals. Usually, it is inserted in devices such as switches, routers or network interface cards which provide one or more transceiver module slot. There are many optical module types (shown in the figure below), such as SFP, X2, XENPAK, XFP, SFP+, QSFP+, CFP and so on.

Optical Modules

A patch cable is a electric or optical cable terminated with connectors on both ends. It is used to connect one electronic or optical device to another for signal routing. Optical patch cables are now widely used in data centers for data transmission. They have different connector types (shown in the figure below), like LC, SC, ST and FC, etc. They also have different fiber types, like single-mode patch cable, multimode patch cable, simplex patch cable, duplex patch cable and so on.

Optical Connectors

Selecting Patch Cable for Optical Module

There are three basic aspects that you have to consider when selecting patch cable for optical module—transmission media, transmission distance and rate as well as module interface. Transmission media can be optical fiber or copper; transmission rate will decrease as the transmission distance increases in the fiber optic cables; duplex SC and LC interfaces are usually employed, and some optical modules often use MPO/MTP interfaces. Let’s take Cisco GLC-LH-SM Compatible 1000BASE-LX/LH SFP Transceiver for example, and its detailed information is shown in the table below. From the table, we can easily find that this GLC-LH-SM 1000BASE-LX/LH SFP Transceiver can transmit and receiver data signals over SMF with LC duplex connector and operating at 1310nm wavelength. So when connecting two transceivers of this type, we are supposed to use a single-mode patch cable with LC-LC connector.

Detailed Information of Cisco GLC-LH-SM Compatible 1000BASE-LX/LH SFP Transceiver

Installing or Removing Optical Module

After knowing how to select patch cable for your optical module, let’s move on to how to install or remove optical module effectively. First, there are several warming tips about installing or removing optical module:

  • To prevent the cables, connectors and the optical interfaces from damages, you must disconnect all cables before installing or removing an optical module.
  • Remember to protect the optical modules by inserting clean dust plugs into them after the cables are removed. Avoid getting dust and other contaminants into the optical ports of your optical modules.
  • Frequently remove and install an optical module can shorten its useful life. Thus, you should remove or insert it unless it is necessary.
  • Optical modules are sensitive to static, so be sure to use an ESD wrist strap or comparable grounding device during both installation and removal.
Installing Procedure

Step 1. Attach an ESD (electric-static discharge) preventive wrist strap to your wrist and to the ESD ground connector or a bare metal surface on your chassis.
Step 2. Remove the optical module from its protective packaging.
Step 3. Check the label on the module body to verify that you have the correct module for your network.
Step 4. Align the optical module in front of the socket opening.
Step 5. Insert the optical module into the socket until the module makes contact with the socket connector.

Removing Procedure

Step 1. Attach an ESD-preventive wrist strap to your wrist and to the ESD ground connector or a bare metal surface on your chassis.
Step 2. Disconnect and remove interface cable from optical module.
Step 3. Immediately install the dust plug into the module’s optical bore.
Step 4. Slide the optical module out of the socket connector.
Step 5. Place the removed optical module into an antistatic bag.

In fact, different types of optical modules have different structures, so remember to follow the instruction when inserting them into the socket or removing then out of the socket connector.


Optical module, essentially completing the conversion of data signals between different media, can realize the connection between two switches or other devices. It has become the key component in today’s transmission network. Therefore, it is helpful to learn how to select patch cable for an optical module as well as install and remove an optical module, even though you are not a professional telecom engineer. I hope this passage can help you during the operation.