What is Optical Circulator in Optical Communication?

Optical circulator is a multi-port optical device with nonreciprocal property. It is based on the nonreciprocal polarization of an optical signal by Faraday effect. When an optical signal is input from any port, it can be output from the next port sequentially with very low loss, and the loss from this port to all other ports is very large, so these ports are not communicating with each other.

That means that optical circulator is a three- or four-port optical device designed such that light entering any port exits from the next. If light enters port 1 it is emitted from port 2, but if some of the emitted light is reflected back to the circulator, it does not come out of port 1 but instead exits from port 3. This is analogous to the operation of an electronic circulator.

 

Fiber-optic circulators are used to separate optical signals that travel in opposite directions in an optical fiber, for example to achieve bi-directional transmission over a single fiber. Because of their high isolation of the input and reflected optical powers and their low insertion loss, optical circulators are widely used in advanced communication systems and fiber-optic sensor applications.

 

Optical circulators are non-reciprocal optics, which means that changes in the properties of light passing through the device are not reversed when the light passes through in the opposite direction. This can only happen when the symmetry of the system is broken, for example by an external magnetic field. A Faraday rotator is another example of a non-reciprocal optical device, and indeed it is possible to construct an optical circulator based on a Faraday rotator.

 

Structure Principle
It consists of a Faraday rotator and two polarizing prisms on both sides. When polarized light passes through a Faraday rotator, its polarization plane can rotate 45°under the action of an external magnetic field. As long as the optical axes of the two polarizing prisms are set at an appropriate angle to each other, the insertion loss of the inter-connected optical paths can be very low and the isolation of the disconnected optical path is very large.

 

The optical circulator can also be formed by utilizing the characteristics of the single-mode fiber will produce the Faraday rotation effect under the action of an external magnetic field. The insertion loss and isolation of the polarization-independent optical circulator are independent of the polarization state of the incident light.

 

Technical Parameters
The technical parameters of optical circulator include insertion loss, isolation, crosstalk, polarization dependent loss(PDL), polarization mode dispersion(PDM) and return loss, etc. The definitions of insertion loss, isolation, polarization dependent loss and polarization mode dispersion of optical circulators are basically the same as those of optical isolators, except that for an optical circulator, it refers to a specific index between two adjacent ports.

What Is Optical Communication?

 Optical communication is any type of communication in which light is used to carry the signal to the remote end, instead of electrical current. The transmitted information is firstly converted into an electrical signal in the transmitting end, and then the electrical signal is modulated onto the laser beam emitted by the light source, so that the light intensity changes with the frequency of electrical signal. Based on the principle of total internal reflection, the light signal is transmitted in optical fiber.

Due to the loss and dispersion of the optical fiber, the optical signal will be attenuated and distorted over a long distance transmission. It is necessary to amplify the attenuated signal at the optical repeater and repair the distorted waveform. At the receiving end, the detector converts the optical signal into an electrical signal after receiving it, the original information will be restored after demodulation. 

 

Advantages of Optical Transmission

• Large Capacity and Long Transmission Distance
• Small Size, Light Weight, Long Life and Low Cost
• High Insulation and High Voltage Resistant
• High Temperature and Anti-corrosion
• Strong Adaptability and High Confidentiality

 

Optical communication consists of a series of optical communication devices. There are active devices and passive devices. Optical active devices are key devices in optical communication systems that convert electrical signals into optical signals or convert optical signals into electrical signals. Optical passive devices mainly include optical fiber patch cables, wavelength division multiplexers(WDM), optical splitters, optical switches, optical circulators and optical isolators, etc.

 

Optical fiber patch cord is a fiber optic cable with connectors at both ends to realize the connection of optical path. The cable with only one connector is called pigtail.

In fiber-optic communications, wavelength-division multiplexing (WDM) is a technology which multiplexes a number of optical carrier signals onto a single optical fiber by using different wavelengths. This technique enables bidirectional communications over a single strand of fiber, also called wavelength-division duplexing, as well as multiplication of capacity.

 

A optical splitter is an optical device that splits a beam of light in two or more. There are two types of splitters: FBT couplers and PLC splitters.

 

Optical Switch is a device that switches or amplifies optical signals. It is mainly used to realize the physical switching of optical signal or other logical operation in optical path, and is often used as the key device of optical cross connection (OXC) technology to switch optical path.

An optical circulator is a three- or four-port optical device designed such that light entering any port exits from the next. This means that if light enters port 1 it is emitted from port 2, but if some of the emitted light is reflected back to the circulator, it does not come out of port 1 but instead exits from port 3.

 

An optical isolator is an optical component which allows the transmission of light in only one direction. The working principle is based on the non-reciprocity of Faraday rotation. Optical Isolator is typically used to prevent unwanted feedback into an optical oscillator, such as a laser cavity.

Rack Optical Switch, Rackmount Fiber Optical Switches|GlsunMall

GLSUN Rackmounted optical switch is a kind of optical path control and switching device to choose working optical path switch manually with button and also control optical path switch or scan in frequency the optical switch which need to be monitored with RS 232 port and Ethernet port.

GLSUN MEMS 1xN Optical Switch

GLSUN MEMS 1xN optical switch is based on micro-electro-mechanical system, which uses optical micro mirrors or optical micro-mirror arrays to change the propagation direction of light beam to achieve optical path switching. This 1xN MEMS Optical Switch is mainly used for DWDM networks, channel monitor and R&D in laboratory.

All-Optical Switches: MEMS vs Mechanical Switches in Fiber Optical Network

In the optical fiber communication system, the Optical Switch (OS) is mainly used to realize the physical switching of optical signals or other logical operations in the optical path, and is mostly used in the optical cross-connect (OXC) technology as a key device for switching the optical path.

Types of Optical Switches

According to the number of input and output ports of the optical switch, it can be divided into 1x1, 1x2, 1xN , 2x2, 2xN, MxN, etc. Thus optical switch has one or more transmission windows for different uses in different occasions.

Classified from the manufacturing process, optical switches can be divided into mechanical optical switches, thermo-optical switches, acousto-optical switches, electro-optical switches, magneto-optical switches, liquid crystal optical switches and MEMS optical switches, etc. Among them, mechanical optical switches and MEMS optical switches are two widely used optical switches.

Mechanical Optical Switches

The mechanical/optomechanical switch may be regarded as the oldest type of optical switches. The working principle of the mechanical optical switch is to redirect the optical signal by physically moving the optical fiber with the aid of a mechanical device. By moving the prism or the directional coupler, the light at the input end is directed to the required output port. There are three main types of mechanical optical switches: one is to use prism to switch the optical path technology, the other is to use mirror switching technology, and the third is to switch the optical path by moving optical fibers. Read more on All-Optical Switches: MEMS vs Mechanical Switches in Fiber Optical Network.

Passive Fiber Optical Components, Devices, Solutions|GlsunMall

GLsun provides full range of passive fiber optical components, devices such as optical plc splitters, circulators, isolators, attenuators and WDM devices & modules for higher capacity fiber network transport in business, data center, and telecommunication operation. 

What are WDM, CWDM, CCWDM, DWDM, FWDM, LWDM Multiplexer

 What is WDM

WDM (optical Division Multiplexing) is the technology to combine two or more optical carrier signals of different wavelengths (carrying various information) at the transmitting end through a Multiplexer coupled to the same optical fiber for transmission. At the receiving end the optical signals of various wavelengths are separated by Demultiplexer, and then restored to the original signal by the optical receiver for further processing. The main purpose of WDM is to increase the bandwidth capacity of optical fibers. Therefore, WDM systems are widely used by telecom operators to expand capacity through WDM without laying more optical fibers.

What is CWDM, CCWDM, DWDM, FWDM, LWDM

WDM solutions include CWDM (Coarse Wavelength Division Multiplexing), CCWDM (Compact Coarse Wavelength Division Multiplexing), DWDM (Dense Wavelength Division Multiplexing), FWDM (Filter Wavelength Division Multiplexing) and LWDM (LAN Wavelength Division Multiplexing).

CWDM (Coarse Wavelength Division Multiplexer)

CWDM consists of 18 different wavelength channels spaced 20 nm apart from 1270nm to 1610nm. CWDM supports fewer channels than DWDM because it is compact and cost-effective, making it an ideal solution for short range communication. The main advantage of CWDM system is its low cost, which is reflected in filters and lasers. The wide wavelength interval of 20nm demands low technical requirement for laser and simplified structure of optical multiplexer/demultiplexer for CWDM. With simplified structure and improved yield, the cost is reduced.

DWDM (Dense Wavelength Division Multiplexer)

The channel spacing of DWDM is 1.6/0.8/0.4 nm (200GHz/100 GHz/50 GHz), much narrower than that of CWDM. Compared with CWDM, DWDM has dense wavelength spacing and can support 8 to 160 wavelengths on one optic fiber, very sui for long-haul transmission. Combined with EDFA, DWDM system can work within a range of thousands of kilometers. Read more on WDM, CWDM, CCWDM, DWDM, FWDM, LWDM Multiplexer.