Month: October 2022

Why Do We Need Polarization Maintaining Fibers?

Polarization maintaining fibers has been around since the development of fiber optics in the mid 20th century.

In fact, these fibers are considered to be the next generation of fiber optic technology with capabilities such as high bandwidth, low loss, and high temperature stability.

In order to understand this concept, you must first have an understanding of what polarization is and how it works in fiber optics.

What is Polarization?

Polarization is a fundamental property of electromagnetic waves, which have oscillating electric and magnetic fields. This phenomenon occurs in light waves and radio waves, for example.

Light that is polarized can be described as having an electric field vibrating at right angles to its direction of travel, or an electric field vibrating parallel to its direction of travel.

Light with an uneven distribution of polarization (i.e., light that has both vertical and horizontal components) can be said to be unpolarized.

What is Polarization Maintaining Fibers?

A polarization-maintaining fiber (PM Fiber) is a specialty single-mode fiber. Normally, single-mode fibers can carry randomly polarized light. In contrast, PM fiber propagates a single polarization of light.

Polarization-maintaining fibers maintain linearly-polarized light waves during propagation and do not cross-couple optical power between polarizations.

Some fiber optic components require polarized light input, such as external modulators. This polarization-maintaining feature plays a crucial role in these components.

In order to achieve this characteristic, stresses are induced in the material during the manufacturing process. PMFs come in two types: linear polarization maintaining fibers (LPMFs) and circular polarization maintaining fibers (CPMFs)

Uses of Polarization Maintaining Fibers

A PMF fiber optic cable is used in many applications. In fact, a PMF fiber optic cable might be what you are using to read these words right now!

The most common applications of PMF optical cables include lightwave transmission, telecommunications, and medical equipment.

Many telecommunications companies use PMF optical cables to transmit information over long distances in order to support communication between different countries.

Common medical devices that utilize fiber optics are sonography devices and endoscopes.

Ways of Realizing Polarization-maintaining Fibers

First, a polarization preserving fiber (PPF) has three layers: core, clad, and coating. Inside an optical fiber is a cavity known as core that is surrounded by a cladding.

There are also two polarizations in fiber optics – linear and circular polarization. Circular polarization states that when light propagates through a medium with time-varying ellipticity, its direction rotates continuously around an axis parallel to the propagation direction.

Cross Section of Polarization Maintaining Fibers

Polarization-maintaining fibers (PMF) or polarization-maintaining optical fibers (PMOF) are optical fibers which have a property that preserves the polarization state of light as it travels through them.

This is an important feature for applications in areas such as telecommunications and fiber-optic gyroscopes, and is usually provided by intrinsic material properties (such as birefringence), by inner cladding layers, or by external polarization controllers.

Conclusion

Polarization-maintaining fibers are well known for their ability to allow different polarized components (vertical and horizontal) to be transmitted through the fiber simultaneously. Their applications range from fiber optic sensing to interferometry to slab dielectric waveguides.

A Brief Guide on Optical Isolators, Their Types, and Working

Michael Faraday established that the optical isolator operations are based on Faraday Effect in 1842. According to Faraday Effect, the polarized light plane turns when light energy propagates through the glass that can be exposed to a magnetic field. The direction of rotation of the plane is based on the magnetic field as an alternative to the light transmission direction.

Optical devices and connectors that are used in a fiber optic system also cause some effects such as the absorption of energy and reflection of the optical signal on the output of the transmitter. These effects can cause the light energy to be reproduced back at the supply, which in turn causes interruption or obstruction in the supply function.

To overcome such interference effects, we need optical diodes, also called optical isolators.

What is an optical isolator?

An optical isolator goes by multiple names such as an optical diode, photocoupler, and optocoupler. An optical isolator is a magneto-optic device designed specifically to allow the transmission of the light signal in one direction only.

Due to its functionality, it plays a key role when you need to prevent unnecessary feedback to an optical oscillator, also called a laser cavity. The working of this device mainly depends on Faraday Effect, which plays an important role in the main component, namely the Faraday rotator.

How does an optical isolator work?

An optical isolator is composed of three main components, namely, a Faraday rotator, an input polarizer, and an output polarizer. When a light signal passes through an input polarizer in the forward direction, it turns into polarized light with the vertical plane. The function mode of this optical device is classified into two types depending on different directions of light such as forward mode or backward mode.

In forward mode, the light signal enters an input polarizer and becomes linearly polarized. When this linearly polarized light signal passes through the Faraday rotator, the Faraday rotator rod will turn 45 degrees, allowing the linearly polarized signal to leave the output polarizer at 45 degrees.

In backward mode, as the light signal rotated by 45 degrees enters the output polarizer, it again turns by 45 degrees in a similar path when passing through the Faraday rotator. After that, 90 degrees polarized light turns into a vertical plane toward the input polarizer and hence, cannot leave the isolator. At this point, the light beam is either absorbed or reflected.

What are the different types of optical isolators?

Based on working, optical isolators are categorized into different types:

  • Polarized Type Optical Isolator: This type of isolator utilizes the polarization axis to transmit light in one direction. It allows light to travel in the forward direction and stops light to transmit back. In this category, you can find polarization-dependent isolators and polarization-independent isolators.
  • Composite Type Optical Isolator: It is a polarization-independent polarizer that is often used in EDFA that has different components such as WDM, erbium-doped fiber, pumping diode laser, and more.
  • Magnetic Type Optical Isolator: It is a polarized optical isolator that pressurizes the magnetic element of a Faraday rotator that works on the Faraday Effect.

Based on the amount of power they can handle, optical isolators can be categorized into two types:

  • High-power isolator: A high-power optical isolator is the optical passive component that allows the transmission of light in one direction and can handle high levels of power. One example of a high-power isolator is a 30Watt 1064nm high-power isolator.
  • Low-power isolator: A low-power optical isolator is the optical passive component that works the same as a high-power isolator but operates at low power. For example:  2Watt 980 PM optical isolator  

If you need optical isolators for your project or application, contact DK Photonics no matter your requirement is for low-power isolators or high-power isolators.

How does a fiber bandpass filter improve the operation of fiber amplifiers?

Optical fiber amplifiers, such as erbium-doped fiber amplifiers (EDFA), are widely used in fiber optic communication systems. Their main function is to recover or amplify the strength of optical signal after it has been traveled or transmitted over a certain distance.

Traditionally, to recover the optical signal, electronic amplification was used where the transmitting optical signal was first converted into an electrical signal which was then amplified and then converted back into the optical signal. This practice made the overall amplification process of an optical signal costly and complicated. This process has been now simplified by EDFAs.

How does an erbium-doped fiber amplifier work?

EDFA modules, which are basically passive amplifiers, use an erbium-doped fiber so that the need for conversion of optical signals into electrical signals and then back into optical signals is eliminated completely.

At present, when it comes to optical amplification, an optical signal is amplified within the optical fiber by a laser that operates at a wavelength of 980nm or 1480nm. This laser excites erbium atoms, which then emit a large number of photons when triggered by a much weaker incoming optical signal at the same wavelength as the incoming optical signal.

This entire process results in an amplification of the input optical signal at the output of an EDFA.

Why does an EDFA need an optical filter?

Most telecom wavelengths function and operate in the C-band (1520nm-1570nm) or the L-band (1570nm-1620nm). That’s why the pump laser that acts upon the optical signal disrupts the precise wavelength, which is a significant issue in a fiber that accepts multiple communication channels.

In traditional EDFAs, a pair of filter components was used to rectify the EDFA’s output signal. A GFF (Gain Flattening Filter) or fiber bandpass filter is used to flatten or even out the outgoing amplified optical signal. This filter operates in accordance with a 980nm-blocking or 1480nm-blocking wavelength-division multiplexer (WDM). A WDM is also used to minimize the interference caused by the pump laser.

A thin-film fiber bandpass filter is designed to block or pass wavelengths of a certain band. While filters are designed using different technologies, one of the best filters is a fiber bandpass filter that is made based on environmentally stable thin-film filter technology.

You can easily implement this to block unwanted noise or unwanted signals in fiber amplifiers, as well as fiber laser systems.

Being an optical passive component, it is also characterized by high isolation, low insertion loss, high return loss, and excellent environmental stability. Some filters are also designed to handle high-power fiber amplifiers, fiber lasers, high-speed communication, and instrumentation systems.

If you are looking for high-quality fiber bandpass filters, contact DK Photonics. We are the leading manufacturer of optical passive components, including fiber bandpass filters for different operating wavelengths.

What does a DWDM Mux Demux Device do?

DWDM is an acronym for Dense Wavelength Division Multiplexing. DWDM is a multiplexing technology based on optic fibers and is specifically designed to increase the bandwidth of existing fiber networks and infrastructure. This technology combines optical signals from different sources and multiplexes them over a single optical cable while ensuring that all data streams remain separate.

In DWDM, each individual light wavelength carries a separate optical signal. Here, the term “dense” refers to the fact that this technology can accommodate up to 80 different wavelengths, where each wavelength is about 0.8nanometer wide and propagates along with other optical signals without getting mixed.

To enable this multiplexing technology and increase the bandwidth of your fiber network, you need to buy DWDM Mux Demux devices. These devices allow you to combine (multiplex – Mux) different optical signals over a single optical fiber on one end and split (demultiplex – Demux) optical signals on the other end. As a result, the implementation of DWDM Mux Demux devices increases the capacity of a fiber network without the installation of additional expensive optical fibers.

How do DWDM mux demux devices improve fiber networks?

Fiber optical cables have become the backbone of high-speed internet networks and become a standard for the telecommunications industry. DWDM mux demux devices allow enormous amounts of data to traverse along a single network link by creating multiple virtual fibers, thereby, multiplying the capacity of the physical medium i.e. fiber optical cables.

Since data flows through different wavelengths, the streams or channels don’t get mixed up or interfere with each other. Hence, the use of DWDM Mux Demux devices ensures the integrity of data passing through them. It is the significant increase in network capacity due to DWDM technology that enables security partitioning or separate tenants in the same data center.

As it allows telecommunications and cable companies to handle so much data, DWDM mux demux devices have become immensely popular in the industry. Any company that runs densely populated data centers such as hyperscale cloud service providers or collocation providers with dense multi-tenant spaces can benefit from the purchase of DWDM mux demux devices.

How does a DWDM Mux Demux device work?

To understand the working of a DWDM mux demux device, you need to know how dense wavelength division multiplexing technology works. DWDM has tighter or narrow wavelength spacing that allows the adjustment of more channels onto a single fiber. It is better for systems where there are more than eight active wavelengths per fiber.

Since DWDM can finely divide the spectrum, it can easily fit more than 40 channels into the C-band frequency range. DWDM implemented in optical fiber systems today can achieve a throughput of 100Gbps. When DWDM is deployed in network management systems and add/drop multiplexers, carriers can adopt optically based transmission networks. This is what helps you meet the growing demand for increased bandwidth at a significantly lower cost.

Do you need to buy DWDM Mux Demux Devices with standard or custom specifications? Please get in touch with DK Photonics now.

A Brief Guide on the Need and Use of Inline Polarizers

The need for efficient low-loss components that are compatible with optical fibers is growing quickly. An all-fiber inline polarizer is therefore a more desirable alternative that can be placed at appropriate intervals along communication links. It works by coupling optical energy traveling in the fiber to a surface Plasmon on a metallic film, which is deposited to the surface of the fiber.

What is polarization and why does polarization of light matter?

Polarization is a special property of electromagnetic waves that refers to the behavior of the electric field with time. If the electric vectors of a group of transverse waves (longitudinal waves cannot be polarized) are at random angles (i.e. in all or any directions), a light is said to be unpolarized. If the electric vectors of transverse waves have the same angles, the light is said to be polarized.

Polarization is desirable in many components and systems because the use of unpolarized light leads to interference and performance issues. 

Fiber optics components such as polarizers transmit waves with electric vectors in one plane and the other waves are either reflected or absorbed.

The operational characteristics of many fiber optic systems vary by the polarization of the light travelling in the optical fiber. That is why maintaining polarization is essential in fiber optics communications, optical gyroscopes, and interferometric sensors to prevent signal fading and error.

To obtain a high level of accuracy in measurements, it is important to have the light with just one polarization. Therefore, it is crucial to implement fiber optic polarizers with a high extinction ratio.

Why use in-line polarizers instead of standard polarizers?

Standard polarizing components in optical systems are bulky, which makes it difficult to align the optical axis between components. Besides, using bulky polarizers can result in higher costs, lack of mechanical and thermal stability, and high losses.

Hence, when it comes to maintaining the polarization of the light in the fiber, the most desirable fiber optic component is an in-line polarizer because it has a fiber-like structure, making it easier to align the optical axis between components.

Inline fiber components are more desirable in most fiber optics systems and have been successfully used in beam splitters, faraday rotators, and filters.

What are the different types of fiber polarizers?

The first optical polarizer was made using calcite prism. However, because of the limitations posed by the optical constants of calcite crystal, it was soon replaced by dichroic polarizers. If natural light falls on some homogeneous media and the light is partially polarized either circularly or linearly, such media are called dichroic.

The commercial usefulness and viability of fiber inline polarizers depend on several key aspects of the construction and design.

At DK Photonics, we offer a wide range of fiber polarizers, such as 980nm in-line polarizers, 1030nm in-line polarizers, 1064nm in-line polarizers, 1480nm in-line polarizers, 1550nm in-line polarizers, 2000nm in-line polarizers, 2050nm in-line polarizers, and more.

The Rising Demand for PM Fiber Components in Aerospace and Military Industries

The aerospace and military industries have always been on the priority when it comes to employing advanced technology. That’s why there remains a high demand for fiber optics components, including PM fiber components because of their superior qualities they come with, compared to traditional technology.

According to Aerospace and Military Fiber Optic Market Research Report 2022 published by ResearchAndMarkets.com, the market of fiber optics in the aerospace and military industry is projected to grow at CAGR of 7.0% from 2022 to 2028.

Why do aerospace and military industries need fiber components?

There are many reasons why aerospace industry and defense forces need fiber components. One of the biggest reasons is that they use advanced communication systems to ensure effective and continuous contact between personnel at different sites and the base station.

Hence, both of these industries pose a continuously high demand for technologically enhanced and high-speed communication systems. The prominent benefit of high-speed data transfer solutions is the quick access to real-time information with the minimized scope for data loss.

Besides, commercial airlines have been using long-haul flights because of increasing passenger traffic. They demand high-speed communication and seamless connectivity. Typically, Ethernet has been the preferred choice for network infrastructure protocol among commercial airlines, owing to its superior performance, reliability, and universally accepted open standard.

However, even with Ethernet network connectivity, there are many limitations in transmitting high bandwidth data over longer distances. This prompted the aircraft cabling system manufacturers to venture into the fiber optics cable and components industry.

That’s why aircraft manufacturers and companies that manufacture defense systems now opt for fiber optic solutions. When it comes to high-speed communication systems, non-PM and PM components are better choice than their electrical or electronic counterparts.

What’s trending in the fiber optics industry these days?

As the number of applications of fiber optics components is continuously growing, the performance of PM fiber components is also anticipated to meet the demanding expectations and combat existing challenges.

With standard fibers, we still face many issues. They are too sensitive to fluctuations caused by different things such as material inhomogeneity, environmental changes, and mechanical stress developed due to fiber compression, bending, twisting, and stretching. As a result, it becomes difficult to preserve the polarization state when light propagates through the fiber.

Therefore, 80um PM fiber components are getting more common than traditional 125um PM fiber components. 80um fiber components are getting edge in the fiber optics industry because of their thin diameter. The thin diameter in PM fiber that is used to make PM fiber components offers various benefits such as no tension fused taper in the fiber, on-line adjustment of main axes in PM fibers, and high stability package.

Even though both variants (80um fiber and 125um fiber) are known for offering the same performance and extinction ratios, the reason behind the increasing popularity of 80um PM fiber components is that they are designed to ensure low bend loss at small bend diameters.

So, you will find 80um PM Fiber and 80um PM fiber components trending more in the fiber optics industry these days.

What are the Advantages of High-Power Fiber Lasers?

Undoubtedly, optical fiber has revolutionized the reform of the telecommunications industry. It has replaced traditionally used copper wires and has become the core part of modern communication. 

With optical fiber, the communication system is a kind of communication system with light as an information carrier. The optical fiber transmits information in the form of electrical signals that are transformed into optical signals. 

Due to the wide application of optical fiber in communication, the rapid development of fiber amplifiers and fiber lasers is seen. Other than this, the optical fiber system is used in medicine, sensing, and other fields. 

When we discuss fiber lasers, high-power fiber lasers always take the limelight. But, many people don’t know why it happens. Also, some people haven’t used high-power fiber lasers yet. 

They have a good beam quality 

The high-power laser fibers achieve high brightness laser output because their waveguide structure determines that the fiber laser is easy to obtain single transverse mode output. Also, the fiber laser is little affected by external factors, leading to good beam quality. 

They are highly efficient 

By selecting a semiconductor laser, the fiber laser achieves high optical to optical conversion. The semiconductor laser emits a wavelength that matches the absorption characteristics of doped rare earth elements as the pump source. 

The energy level structure is simple. So, a few phenomena such as up conversion, excited state absorption, and concentration quenching effectively store energy to achieve high-power operations. 

They have a good heat dissipation characteristics 

As a laser gain medium, the fiber laser uses slender rare earth-doped fiber. Also, the surface area and volume ratio of the fiber laser are very large. Compared to solid-state block lasers, the high-power fiber laser is 1000 times faster. The high-power fiber laser has natural advantages in heat dissipation capacity. 

In low and medium power, special cooling of the optical fiber is not needed. But, special cooling plays an important role in high-power fiber lasers. It avoids the decline of beam quality and efficiency caused by thermal effects in solid-state lasers. 

They have a compact structure and higher reliability 

The fiber laser uses a small and soft fiber just like the laser gain medium. The small and soft fiber is conducive to compressing the volume and saving cost. 

Using fused fiber optical products such as fiber Bragg grating, the all-optical fiber can be used as long as the products are fused. The immunity is high to environmental disturbance, high stability, and saves maintenance time and cost. 

The high-power fiber laser is beneficial. You should just know to use it in the right way.