Introduction to Microservice Architecture Using SpringBoot - Part 1

Wavelength-division multiplexing (WDM)

Wavelength-division multiplexing (WDM) is a technology used in fiber optic communication systems to simultaneously transmit multiple optical signals or data streams over a single optical fiber. It enables the efficient utilization of the available bandwidth by dividing the optical spectrum into different channels, each carrying its own unique wavelength.

Working Principle:

WDM operates on the principle of transmitting multiple optical signals at different wavelengths simultaneously over a single fiber. Each optical signal occupies a specific wavelength or frequency band within the optical spectrum. The signals are combined at the transmitter end and then transmitted through the fiber. At the receiver end, the signals are separated based on their wavelengths using a demultiplexer, and each signal is directed to its respective destination.

Types of WDM:

1. Coarse Wavelength Division Multiplexing (CWDM): CWDM uses wider spacing between wavelengths, typically around 20 nm, allowing for a smaller number of channels. CWDM is cost-effective and well-suited for shorter transmission distances, such as metropolitan area networks (MANs) or access networks.

2. Dense Wavelength Division Multiplexing (DWDM): DWDM utilizes closely spaced wavelengths, typically with spacing of 0.8 nm or less, enabling a high number of channels to be transmitted over a single fiber. DWDM systems can support dozens or even hundreds of channels and are used for long-haul and ultra-long-haul transmission over substantial distances, such as transoceanic links.

Components of WDM Systems:

1. Transmitters: The transmitters in a WDM system combine multiple optical signals onto different wavelengths or channels using optical multiplexers. Each signal is modulated onto its corresponding wavelength, and the combined signals are then launched into the fiber.

2. Fiber Optic Cable: The optical signals are transmitted through the fiber optic cable, which acts as the transmission medium. The fiber should have low dispersion characteristics to minimize signal distortion and ensure proper transmission over long distances.

3. Multiplexers/Demultiplexers: Multiplexers are used to combine the optical signals onto the fiber, and demultiplexers are used to separate the signals at the receiving end. Multiplexers and demultiplexers can be implemented using various technologies, such as thin-film filters, arrayed waveguide gratings (AWGs), or fiber Bragg gratings (FBGs).

4. Optical Amplifiers: Optical amplifiers, such as erbium-doped fiber amplifiers (EDFAs) or Raman amplifiers, are used to amplify the optical signals at regular intervals to compensate for transmission losses and maintain signal quality.

Applications:

WDM technology is widely used in various applications, including long-haul and metro optical networks, submarine communication systems, data centers, and high-speed internet backbones. It allows for the efficient utilization of fiber optic infrastructure, enabling the transmission of large amounts of data over long distances and supporting high-capacity communication links.

Advantages:

1. Increased Capacity: WDM enables the transmission of multiple signals simultaneously over a single fiber, significantly increasing the capacity of the network.

2. Scalability: WDM systems can be easily upgraded and expanded by adding more channels or wavelengths to meet growing bandwidth demands.

3. Cost-Effective: WDM allows for the consolidation of multiple communication links onto a single fiber, reducing the need for additional fibers and associated infrastructure.

4. Flexibility: WDM supports different data rates and protocols, allowing for the integration of various services, such as voice, data, and video, over a common fiber infrastructure.

Dense Wavelength Division Multiplexing (DWDM) DWDM: 

DWDM (Dense wavelength – division multiplexing) is a data transmission technology having very large capacity and efficiency. Multiple data channels of optical signals are assigned different wavelengths, and are multiplexed onto one fiber. DWDM system consist of transmitters, multiplexers, optical amplifier and demultiplexer. 

DWDM used single mode fiber to carry multiple light waves of different frequencies. DWDM system uses Erbium – Doped Fiber Amplifiers (EDFA) for its long haul applications, and to overcome the effects of dispersion and attenuation channel spacing of 100 GHz is used.DWDW is short for dense wavelength division multiplexing. It is an optical multiplexing technology used to increase bandwidth over existing fiber networks. DWDM works by combining and transmitting multiple signals simultaneously at different wavelengths on the same fiber. It has revolutionized the transmission of information over long distances. DWDM can be divided into passive DWDM and active DWDM. This article will detail these two DWDM systems.

Passive DWDM Passive 

Passive DWDM systems have no active components. The line functions only due to the optical budget of transceivers used. No optical signal amplifiers and dispersion compensators are used. Passive DWDM systems have a high channel capacity and potential for expansion, but the transmission distance is limited to the optical budget of transceivers used. The main application of passive DWDM system is metro networks and high speed communication lines with a high channel capacity. 

Active DWDM 

Active DWDM systems commonly refer to as a transponder-based system. They offer a way to transport large amounts of data between sites in a data center interconnect setting. The transponder takes the outputs of the SAN or IP switch format, usually in a short wave 850nm or long wave 1310nm format, and converts them through an optical-electrical-optical (OEO) DWDM conversion. When creating long-haul DWDM networks, several EDFA amplifiers are installed sequentially in the line. The number of amplifiers in one section is limited and depends on the optical cable type, channel count, data transmission rate of each channel, and permissible OSNR value. The possible length of lines when using active DWDM system is determined not only with installed optical amplifiers and the OSNR value, but also with the influence of chromatic dispersion—the distortion of transmitted signal impulses, on transmitted signals. At the design stage of the DWDM network project, permissible values of chromatic dispersion for the transceivers are taken into account, and, if necessary, chromatic dispersion compensation modules (DCM) are included in the line. DCM introduces additional attenuation into the line, which leads to a reduction of the amplified section length.