Tag: passive DWDM MUX

DWDM Solutions for Arista 7500E Series Switches

Nowadays, the deployment of DWDM solution has been hotly debated in many enterprise networks, especially in the new Lay2 and Lay3 equipment like Arista 7500E series switches. For many enterprises, DWDM network solutions are undoubtedly the best choices of action, because they can provide a scalable and elastic solution for the enterprise that offered high bandwidth and data separation. This article will demonstrate DWDM solutions to Arista 7500E switches which are the foundation of two-tier open networking solutions for cloud data centers.

Analysis of DWDM System

DWDM (Dense Wavelength Division Multiplexing) is a technology allowing high throughput capacity over longer distances commonly ranging between 44-88 channels and transferring data rates from 100 Mbps up to 100 Gbps per wavelength. For intra-datacenter solutions, an endpoint connection often uses multimode (850 nm) for short ranges and single mode (1310 nm) for longer ranges. The DWDM node converts this local connection to a channelized frequency or wavelength, which is then multiplexed with other wavelength and transmitted over a single fiber connection.

A key advantage of DWDM is that it’s bitrate independent. DWDM-based networks can transmit data in IP, ATM, SONET, SDH and Ethernet. Therefore, DWDM systems can carry different types of traffic at different speeds over an optical channel. Voice transmission, email, video and multimedia data are just some examples of services which can be simultaneously transmitted in DWDM systems.

DWDM multi-channel Mux/Demux

Arista 7500E 100G DWDM Line Card

With full support for Layer2 and Layer3 protocols, Arista 7500E series switch is the ideal option for the network spine for two tier data centers applications. Arista 7500E especially provides the perfect resolution for high bandwidth Metro and long-haul DCI solutions with the 6-port DWDM line card. It has great advantage to migrate from existing 10G DWDM to 100G coherent line side modules. The 7500E series DWDM line card provides six 100G ports with coherent 100G tunable optics, which enables customers to connect directly into existing WDM MUX module without the need to add transceivers, which can save cost and space to a large extent. The coherent optics use C-band region wavelengths and offer a cost efficient solution for up to 96 channels of 100Gb over a single dark fiber pair.

Use Cases for Arista 7500E DWDM Card
    • Less Than 80 km Dark Fiber Connection
      For distance less than 80 km, Arista 7500E switch with DWDM line cards can directly terminate a dark fiber connection with a pair of passive DWDM Mux, thus achieving a point-to-point connection between two locations.

Dark Fiber Connection

  • Between 80 km and 150 km Connection
    For distance greater than 80 km but less than 150 km, losses occurred during the process of transmission should be considered. In order to boost the power level, an EDFA (Erbium Doped Fiber Amplifier) is used to gain flatness, noise level, and output power, which is typically capable of gains of 30 dB or more and output power of +17 dB or more. With the use of EDFA, the signal can be boosted into a certain power level, thus achieving distances of up to 150 km.
Conclusion

The Arista 7500E series DWDM solution offers a cost-effective solution for transporting scalable and massive volumes of traffic, and enhances the 7500E system by providing high performance 100G DWDM port density with the same rich features and dedicated secure encryption in compact and power-efficient systems. Enterprises can easily migrate existing metro and long-haul DWDM networks to add new 100G capacities, thus expanding Layer2 and Layer3 services.

Originally published at http://www.china-cable-suppliers.com/dwdm-solutions-arista-7500e-series-switches.html

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Passive DWDM vs. Active DWDM

To keep pace with the rapidly growing volumes of data-network traffic driven by the growth of the Internet, service providers are always looking to increase the fiber capacity and wavelength spectral efficiency in their networks. DWDW (dense wavelength division multiplexing) 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 which will be illustrated in this article.

Passive DWDM

“Passive” refers to the passive DWDM MUX/DEMUX element which is an unpowered, pure optical equipment. Passive DWDM systems have no active components, which means that no optical signal amplifiers and dispersion compensation modules (DCM) are used. The DWDM passive link is only determined by the optical budget of transceivers used. Passive DWDM system has a high channel capacity and potential for expansion, but the transmission distance is limited to the optical 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 system is built from transponders, providing full optical demarcation point agnostic to the routers, switches and ADMs within the network. Active DWDM offers 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. In long-haul DWDM networks, several EDFAs are installed sequentially in the line. The number of amplifiers in one section is determined by the fiber cable type, channel count, data transmission rate of each channel, and permissible OSNR value.

active DWDM

Besides, the maximum transmission distance of the active DWDM system also depends on the influence of chromatic dispersion—the distortion of transmitted signal impulses. When designing a DWDM network project, permissible values of chromatic dispersion for the transceivers should be considered, and, if necessary, chromatic dispersion compensation modules are included in the line. DCM fixes the form of optical signals that are deformed by chromatic dispersion and compensates for chromatic dispersion in fibers.

Choosing passive or active DWDM system depends on your requirements and current setup. Because both of them have pros and cons.

Passive DWDM
Pros:
1. Inexpensive – As mentioned above, less components are required, and less engineering time is required.

2. INITIAL Setup – Because of the colored optics there isn’t a need to tune wavelengths for all of your connections. It’s a matter of matching your colored optics and plugging it.

Cons:
1. Scalability – you are limited to colored optics, and less wavelengths on the transport fiber. As you grow, you would be required to have more passive devices. Furthermore, with the more passive devices, you have more difficulty to manage. And you will have to start managing the same wavelength on multiple passive devices and they could be serving different purposes on each depending on your setup.

2. Control – If you need to change a wavelength or connection for whatever reason, your option is limited to taking it out of service and disconnecting the physical cabling as the wavelength is tied to the optic.

Active DWDM
Pros:

1. Active can fit a lot more wavelengths (colors) onto a single fiber pair. The composite signal that is sent over a single fiber pair can carry more bandwidth than a passive of the same size, in turn you don’t need as much physical fiber between your two sites (this really only applies if you require that much bandwidth). This is advantageous when distance is a problem because it allows you to get more out of a single leased fiber pair as opposed to passive.

2. Active setups grant you more control over your optical network, you can dynamically re-tune wavelengths without dropping connections (it’s transparent to whatever is riding on that wavelength).

3. Scalability – Active can be easier to scale as your network grows (you can fit more wavelengths on the fiber, see above), but again – we’re talking seriously big iron. I’ll dig into it a bit more below.

Cons:
1. EXPENSIVE – Active DWDM setups are much more expensive compared to passive DWDM. If you don’t have long-distance requirements, don’t choose active DWDM.

2. Configuration – Depending on your vendor, configuration can be a serious undertaking, and require a solid understanding of optical networks. There are many more components in active builds.

Conclusion

Most of the time, DWDM operates with powered component like transponders. Further, after multiplexing the signals, they typically need active amplification to have any preferred reach. Without this, you’re only going with a relatively short distance, which is not a good value for the expense of DWDM.