Higher non-multiplexing bandwidth: 96 colors DWDM

In a world where more than 90 percent of all business operations are mapped digitally, robust transport networks are required. Cloud computing, artificial intelligence, the Internet of Things, and 4K video streaming require more bandwidth. However, optical fiber lines are limited and must be used efficiently. This is where the proven double-serving technology comes into play.

At first glance, fiber optic cables offer virtually unlimited transmission space. But appearances are deceiving. The Fiber glass It has physical limits, which fortunately are not exhausted. Thus, nonlinear interactions of the optical signals with the waveguide material occur in the optical waveguide. The result is a change in the signal profile (spectral distribution), which becomes illegible above a certain level of interference. The extent to which this occurs depends largely on the noise behavior of the amplifier used and the nonlinear properties of the fibers.

However, these nonlinear phenomena are currently not a real limiting factor for the increasing demand for bandwidth. The limits of transmission over optical fibers are becoming visible in a completely different place – and, thanks to better hardware, they are being explored again and again: that is, where electrical conversion to optical signals and vice versa occurs. Optical transceiver modules are responsible for this, which operate in different formats and at different data rates. For example, it includes the fastest (and most expensive) QSFP-DD transceivers with up to 800 Gbit/s.

There is no double

Of course, this alone is not enough to transfer various applications and existing data volumes data centers attacks. At the same time, the laying or leasing of optical fibers is such an important cost factor, that it is difficult to economically measure bandwidth using the number of fibers.

The solution is found in multiplexing technology: in Wavelength Division Multiplexing (WDM) Many signals are sent simultaneously on a line by converting them to separate wavelengths. Or to put it more simply: signals are transmitted in different colors at the same time and without interference in a single fiber.

Modern data center couplings or Data Center Interconnection (DCI) cannot be imagined without this trick. At present, up to 96 wavelengths can be transmitted on glass fibers using Dense Wavelength Division Multiplexing (DWDM) with channel spacing of 0.4 nm. Thus, the latest DWDM systems achieve data rates of up to 25.6 TB / s per fiber.

DWDM System Structure

Each signal sent is converted into an optical signal in the transceiver connected to the transceiver card. For this purpose, the receiver contains a photodiode that generates a signal of separate wavelength at a constant voltage. Then the signals generated in this way are processed using 3R technology; They undergo (1) resampling, (2) re-amplification, and (3) re-timing of the signal. In this way, signal interference can be compensated for by dispersion and attenuation in advance.

The heart of WDM technology is the multiplexer (de): as a transmitter, it collects individual signals. As a receiver, it splits the complex incoming signal into its original fundamental wavelengths. Typically, a series of cascading thin-film filters is used, which produces the desired filter effect across the thickness of the dielectric and the material. Larger units use an array waveguide (AWG) grid to direct light to different lines in a wavelength-sensitive manner.

Muxponders are also frequently encountered in DWDM systems. This is a synthetic term consisting of a “transponder” and a “transmission multiplexer”. Such modules can convert several low-bandwidth input signals into a single signal in the larger container structure of the outgoing signal. Thanks to this mapping, signals are aggregated without loss of throughput.

Other processes such as Forward Error Correction (FEC) and a Layer 1 hardware-based AES 256-bit encryption Ensure hassle-free and secure data transmission with minimal latency and full data output. Once sensitive data has been sent, the encryption option must always be selected in Datacenter Use, which can also be activated at a later time.
Because there is significant signal attenuation over longer distances, many fiber-optic systems use boosters and preamp units: if the OSNR is below a certain threshold, the signal can no longer be read. In most WDM systems, so-called erbium fiber laser amplifiers (EDFA) are used, which use a laser to excite erbium electrons, which then emit photons.

A management card (NMS) with active monitoring and a web interface, redundant power supplies, and the branch circuit itself complements the WDM system.

Increase transmission rates thanks to multiplexing

Advances in the development of new transceiver modules and ultra-fast multi-protocol cards with integrated AES 256 Layer 1 encryption show that multiplexing technology is not yet exhausted. On the contrary: more powerful transmission systems can be expected in the coming years to meet the increasing demand for bandwidth.