Day: July 3, 2019

Role of an In-Line Polarizer in Communication System

In the telecommunication industry, the use of optical devices has increased dramatically as they offer high performance, optimum efficiency and excellent reliability. But the truth is that deploying light waves is not easy because they are highly susceptible to noise and interference. Fortunately, these issues can be resolved by the use of fiber optic polarizers. They greatly enhance the signal performance in fiber optic systems by suppressing unwanted interference patterns.

Fiber optic polarizers are placed inline so that the extinction characteristics of the fiber optic cable get improved. Due to their inline placement, these are also called in-line polarizers. The good thing about these polarizers is that they allow the transmission of only one polarization and block the remaining light which has unpolarized states.

So, to maintain the polarization and decrease the degradation in polarization, optical polarizers are necessary. Otherwise, there will be noise interference and the performance of the entire fiber optic system will decrease substantially. An ideal fiber optic inline polarizer is the one which transmits linearly polarized light that has a high extinction ratio and low insertion loss.

Here, linear polarization means the electric or magnetic field is confined to the plane in the direction of wave propagation. Extinction ratio refers to the ratio of the power of a plane-polarized beam transmitted by the polarizer to the transmitted power when polarizer’s axis is perpendicular to the plane of beam and insertion loss is defined as the attenuation caused by the insertion of an optical component.

Characteristics

The light waves transmitted by fiber optic systems are usually characterized by the length of wave i.e. wavelength. The carrier signal is further determined by the signal’s optical power which is measured in dBm or mW.

Wavelength: Human eye can detect wavelengths from 400 to 700 nm which is referred to as visible region. However, fiber optic systems transmit the longer wavelength from red (650 nm) to infrared region. It is caused by the characteristics of the transport medium i.e. the optical fiber. Shorter wavelengths are attenuated due to the scattering effect of light source and they are further attenuated by the absorption bands at specific frequencies.

The main three wavelengths which are used for fiber optic systems are 850, 1300, and 1550nm. 850nm wavelengths are primarily used in plastic optical fiber and multimode fiber. Multimode fiber can also be used to transmit 1300 nm carrier signals, however, single mode fiber can transmit even longer wavelengths such as 1310nm, 1490nm, and 1625nm.

Optical Power: The power of an optical signal is a measure of wavelength and photon density. Fiber optic communication systems use very low power signals. It can be measured in dBm and mW. dBm and mW have logarithmic relationship. The power level of 0 dBm is equivalent to 1 milliwatt.

If you are also searching for fiber optic in-line polarizers, you can easily place an order with a reputed polarizer manufacturer online.

What is CWDM Mux/Demux and what it is used for?

Wavelength Division Multiplexing (WDM) is a technology which allows you to expand the capabilities of your existing fiber optic network without the addition of extra optical fiber. Through this technology, a Mux can multiplex various optical signals of different wavelengths on a single optical fiber without the need for additional optical fiber. This helps a lot in relieving the fiber exhaustion and extending the link capacity.

In general, there are two types of Mux/Demux – CWDM and DWDM. In this blog, we will discuss the CWDM type in detail.

CWDM

CWDM stands for Coarse Wavelength Division Multiplexing. A CWDM Mux/Demux is used to increase the capacity of the fiber in 4, 8, 16, or 18 channels. By incrementing the channel spacing between different wavelengths, this device allows an easier, simple and affordable method to carry up to 18 channels on a single fiber. It is mainly used for providing the flexibility to increase the capacity of existing fiber infrastructure.

Application of CWDM Mux/Demux

This device is widely used in a number of applications such as:

  • WDM network
  • Line monitoring
  • Cellular application
  • Access network
  • Fiber amplifier

Each of the CWDM channels uses 20nm of space and all of them consume most of the operating range of single mode. Every channel carries data independently and there is no effect of one channel on the other channel. This allows network designers to transfer different data rates and protocols to meet the different requirements of different customers without any interference. The usual operating wavelength range for 16 channels varies from 1270 to 1610 nm and the most commonly used CWDM Mux/Demux are the ones which come with 16 or 18 channels.

So, which one you should choose for your application? Let’s find out.

16 Channel vs. 18 Channel CWDM Mux/Demux 

The capacity of a CWDM network largely depends on Mux/Demux. If there are more channels of Mux/Demux, the capacity of CWDM network will also be higher. The channel number of most of the Mux/Demux ranges from 2 to 18. Among these, 16 and 18 channel CWDM Mux/Demux devices are more commonly used in the telecommunication industry. Except for the fact that the latter one provides two more channels than the former, there is no difference between them. Since in CWDM Mux/Demux with 18 channels, the capacity is increased, there will be more insertion loss.

So, there is no such thing about superiority between these two. Which one you should choose depends on your specific requirement and application scenario. If your application involves broader network capacity and scalability, an 18 channel CWDM Mux/Demux is recommended to use, otherwise you can go for 16 channel CWDM Mux/Demux.

All you need to know about polarization maintaining optical circulators: a few major pointers!!

Since several years, Polarization Maintaining Optical Circulator has become an important element in the optical communication system. But these days, its applications have expanded not only in the telecommunication field but also in imaging and medical field.

In this blog, we’ll discuss on Polarization Maintaining Optical Circulator in more detail, but before that let’s know a few basic regarding it.

To begin with, let’s discuss what exactly is an optical circulator?

An optical circulator is mainly a multiple port non-reciprocal passive component. Its function is just similar to that of a microwave circulator, i.e. to transmit the light wave from one port to other with maximum intensity. But, at the same time, it also blocks any light transmission from one port to its previous port. Besides, the entire optical circulator process is based on the non-reciprocal polarization of the Faraday Effect.

What are the features of Polarization Maintaining Optical Circulator?

There are various features of polarization maintaining optical circulator. Mentioned below are a few major ones:

–    It has a high stability

–    It has a low insertion loss

–    It has high reliability

–    It has high optical return loss and so on.

How can optical circulators be categorized?

Optical circulators typically can be categorized into two main streams namely:

–    Polarization-dependent optical circulator, and

–    Polarization independent optical circulator

Polarization-dependent optical circulator is functional only for a light wave with a specific polarization state. This type of optical circulator is used only in some of the applications that mainly include free space communication between crystal sensing and satellites. Whereas the polarization independent optical circulator is independent of the polarization state of light. In the ordinary circulators, the polarization is certainly not maintained, however, there are polarization maintaining optical circulators available, so they can be used on behalf of it.

Besides, they can also be utilized in a wide variety of applications, but depending on its functionality, optical circulators may be divided into two groups:

–    Quasi circulator: In this circulator, the light passes through all the multiple ports, but the light from the last port is lost.

–    Full circulator: In this circulator, the light passes through all the multiple ports in a full circle.

When it comes to circulator’s design, there are many variations, but, all the non-reciprocal rotation designs certainly share the same structure with at least three functional elements namely- non-reciprocal polarization rotation elements, polarization recombining, and splitting elements, as well as polarization dependent beam steering elements.

Finally, we can say that with the large development of advanced optical networks and elements, the application of optical circulators are rapidly growing and new and advanced applications and functionalities are emerging quickly.