Month: September 2021

What Are the Different Uses of Polarization Maintaining Optical Isolators?

Optical reflection is a significant cause of the performance degradation in fiber lasers and amplifiers. This issue can easily be resolved by the use of optical isolators. An optical isolator is a small device designed to transmit optical signals in one direction. It comes in two versions: polarization maintaining optical isolators and polarization insensitive optical isolators.

While both types of optical isolators block any returning light, the insertion loss in a polarization maintaining optical isolator depends on the input polarization.

Polarization Maintaining (PM) Optical Isolators

Polarization Maintaining (PM) optical isolators are simpler and very compact in design and highly suitable for polarization maintaining fiber applications. They are also used in scenarios where an input free space beam of constant polarization passes across the Faraday optics. In both types of applications, the linearly polarized beam from the source is aligned with the transmission axis of an optical isolator.

While most passive optical components are reciprocal, optical isolators are usually non-reciprocal. Meaning, optical isolators allow an optical beam to pass in the forward direction with minimal losses while preventing it to propagate in the backward direction.

Though different types of optical isolators can be found in the market such as all-fiber isolators, fiber-embedded isolators, fiber Faraday rotator isolators, and waveguide-based isolators, the core a typical commercially available optical isolator consists of a Faraday rotator with 45-degree rotation and a pair of birefringent crystals.

Applications of PM Optical Isolators

PM optical isolators are playing an increasingly important role, especially in modern optical transmission systems and fiber optic systems. They are mainly used in applications that are sensitive to unwanted optical reflections and require polarized light. Even a very low optical reflection can cause a significant increase in laser phase noise, intensity noise, and wavelength stability. Hence, the use of optical isolators in such applications becomes inevitable.

Another crucial application of polarization maintaining optical isolator is distributed-feedback lasers that are widely used in transmission systems. The distributed feedback laser frequency is said to be very sensitive to the reflection coupled back to the laser cavity due to the single-cavity mode. Since the laser gain profile is not flat, the frequency fluctuation also leads to power instability. Hence, it becomes quite essential to achieve isolation from the optical circuitry and its reflection.

In some cases, Fabry-Perot lasers may also require isolation from the system to enhance the power stability. When Fabry-Petro lasers have fewer cavity modes, the need for isolation in the system increases even more.

Besides, PM optical isolators are widely used in telecommunications and other areas such as biotechnology and sensing (such as fiber-optic gyros). Plus, you will also find their extensive usage in other applications such as fiber lasers, fiber amplifiers, and fiber sensors.

Everything to Know About Wavelength Division Multiplexing (WDM)

As the name suggests, the wavelength division multiplexing or WDM technique uses different light wavelengths for its processing. In fiber optic transmission, the WDM technology increases the data-carrying capacity by using multiple light wavelengths. In specific, the technology multiplexes several optical carrier signals onto a single optical fiber, using different laser light wavelengths.

People think WDM technology is new in the industry. And thus, they don’t trust the same. But truly speaking, WDM technology was developed many years ago and has been deployed across global networks. Today, technology is used in one form or another to a significant degree.

Classification of wavelength division multiplexing (WDM)

 Coarse wavelength division multiplexing (CWDM) – This is defined by wavelengths, which belong to the International Telecommunication Union (ITU). The wavelengths used in this are from 1270nm to 1610nm within 20nm channel spacing. If compared to dense wavelength division multiplexing (DWDM), the CWDM supports fewer channels. So, it becomes the ideal solution for short-range communications. It’s compact and cost-effective.

Dense wavelength division multiplexing (DWDM) – This is defined by frequencies, which is the member of International Telecommunication Union (ITU). The frequency is usually converted to wavelength for use. DWDM is capable to transport up to 80 channels in the 1550nm region. It allows huge amounts of data to travel in one single network link, so it is ideal for long-haul transmission. It’s tightly packed together. 

Differences between CWDM and DWDM

  • Channel spacing 
  • Transmission distance 
  • Modulation laser 
  • Costs

Applications included in WDM technology 

When buying WDM products online or in stores, you will come across many options. To make your purchase easy, we have listed some applications included in WDM technology. 

  • Wavelength multiplexers– Increases bandwidth capacity on existing fibers 
  • WDM filters– Routes specific wavelengths to monitoring equipment 
  • Add/Drop multiplexers– Adds/drops wavelengths along a network route 
  • Aggregation multiplexers– Manages different service providers on the same fiber

Benefits of WDM technology 

  • Transmits and receives high capacity data, which is a ready-made option for high-bandwidth transmissions
  • Boosts the intensity of optical signals for long-range transmission with the help of Erbium-Doped Fiber Amplifier
  • Ensures transmission transparency because wavelengths are independent and channels don’t interfere with each other 
  • Allows new channels without disrupting the existing traffic services, making the upgrades easier
  • Maximizes the utilization of fibers and helps to optimize overall network investments

Where should you buy WDM products?

The WDM technology will work and deliver quality service only if you get the right WDM products. Whether you are planning to buy WDM products online or offline, you should research in-depth. You should look for one of the reputable suppliers of WDM products. 

 DK Photonics is that one popular name that designs and manufactures high-quality WDM products. The company is headquartered in Shenzhen of China. You can place an order for WDM products online through our website and we will deliver them as early as possible. Our products are cost-effective and we offer the best service in the industry. 

1064nm PM Isolator: Applications, Features, and Specifications

Are you looking for a non-reciprocal fiber optic device that allows the flow of optical power in only one direction? Well, if your answer is yes, then you should consider the 1064 polarization-maintaining fiber optic isolator because it prevents reflections in the backward direction. By using PM fibers, you can maintain the 1064 PM optical isolator state of polarization of the light. Today, you can easily find both PM and non-PM types of these 1064nm optical isolators.

Basics of 1064nm PM Isolator:

This PM isolator is based on the non-reciprocal Faraday Effect – a longitudinal magnetic field generates a rounded birefringence that rotates the alignment of the incoming polarization.

Applications of 1064nm PM isolator

The primary application of the 1064nm polarization-maintaining isolator is to protect the transmission of the laser diode from back reflections. That’s because such reflections increase the noise in the system by disrupting the diode’s operation. The 1064nm PM isolator also enhances the steadiness of fiber amplifiers by lessening the chances of reaction, which can cause undesirable oscillation.

Fiber-Coupled 1064nm PM Isolator:

A fiber-coupled 1064nm PM isolator is a device that works like an optical diode. That is, it transmits in one direction while blocking light in the other direction. You can find such isolators in fiber-coupled form – with input and output coupled to single-mode fibers.

The 1064nm PM isolator is generally positioned at the output of the optical source to avert the light reflection from returning to the source. Moreover, Doped Fiber utilizes the 1064nm PM isolators for avoiding an oscillating behavior.

Here are a few features of 1064nm PM Isolators:

  • Polarization maintaining
  • Low insertion loss
  • High isolation and return loss
  • High reliability and stability

Here are a few Specifications of 1064nm PM Isolator

  • Center Wavelength (nm)   1064
  • Operating Wavelength Range (nm)  ±5-10
  • Top Isolation at 23 ℃ (dB)  30-35
  • Min. Isolation at 23 ℃ (dB)   25-28
  • Max. Insertion Loss at 23 ℃ (dB)  1.2
  • Lowest Extinction Ratio at 23 ℃ (dB)   >20
  • Min. Return Loss (Input /Output) (dB)  50
  • Max. Average Optical Power (W)     0.3~200
  • Max. Peak Power for ns Pulse (kW)   1~50
  • Max. Tensile Load (N)    5
  • Operating Temperature (°C)  -5 to +50
  • Storage Temperature (°C)  -10 to +60

Important Things to Note:

  1. The 1064nm PM isolator can be customized, and the above specifications are subject to change.
  2. Unless specified, the slow axis of the fiber is aligned with the key of the PM fiber connector.
  3. Bare fiber doesn’t support the connector’s weight.

You should consider the 1064nm PM isolator if you’re looking for a high-quality passive device that can transmit the optical signals in one direction and block all the undesirable optical reflections.