How to Save Cost for 500Gbps Metro Network Over Long Distance?

Increasing bandwidth has always been the most important task of telecom engineers. Through decades of research and engineering effort, 40Gbps and 100Gbps solutions have been used for network applications. But 40G and 100G transceivers can’t support too much long distance (QSFP-40G-ER4 for 40 km, QSFP-100G-LR4 for 10 km). How to extend the 500Gbps link to thousands of kilometers in Metro network within limited budget?

Save Fiber Cost–500Gbps Over Single Fiber Cable

Fiber cable cost takes a certain percentage in the whole network budget. Point to point connection needs many cables, while WDM technology take well care of this issue. In a metro network, usually multiple 10Gbps signals are transmitted by the use of DWDM Mux/Demux over a single fiber cable, which can save lots of money on multiple fiber cables and cable management issues. Then how to save cost to transmit 500Gbps signals over single fiber cable?

It sounds unbelievable. But we have the cost-effective solution. As we know, it will cost too much to replace all the current network system for upgrading to higher data rate. To save cost for increasing bandwidth, some producers add an extra port on DWDM Mux/Demux and that is 1310nm or 1550nm port. This port supports 1310nm or 1550nm transceiver. With such port, you can add 1G/10G/40G/100G to the existing DWDM network. For instance, we use 40-channel C21-C60 dual fiber DWDM Mux/Demux with 1310nm port and 1310nm band port for 1G/10G/40G/100G “grey” light. Plug 10G DWDM SFP+ transceivers into 40 channels, the overload is 400Gbps. Once plugging a 1310 40G QSFP+ LR4/ER4, then the total link reach up to 440G (400G + 40G). If install a 100G QSFP28 LR4 transceiver into 1310 port, the whole transport will be 500Gbps (400G + 100G). See this solution realize the goal of saving cost to run such huge network load over a single fiber.

Extend 500G Transmission Distance

Since 500G signals can be transmitted over a single fiber cable, we have another issue to be solved. 500G transmission distance is needed far more than few kilometers in real life, maybe thousand of kilometers. How to extend the transmission distance?

According to IEEE standard, LR4 and ER4 transceivers can support the reach of 10 km and 40 km in the in ideal conditions, not considering fiber loss or connector loss. To extend 500Gpbs transmission distance, we need SOA (Semiconductor Optical Amplifier) and EDFA (Erbium Doped Fiber Amplifier). Add an SOA to support 40G/100GBASE-LR4 transceiver (over 1310 nm). The SOA is used to amplify incoming (Rx) signal on the receiving side of the link. So that the distances can reach up to 60 km. In 10Gbps DWDM networks, the signal transmission distance can be extended to hundreds of kilometers by the use of and EDFA (Erbium Doped Fiber Amplifier).

Recommended DWDM Solutions for 500Gbps Metro Network

ID#	FS Part Number	Description
35887	40MDD-1RU-A1-FSDWDM	40 Ch 1RU Duplex DWDM MUX DEMUX C21 to C60 with 1310nm Port and Monitor Port
14491	DWDM-SFP10G-40	10GBASE 100GHz DWDM SFP+ 40km, LC Duplex Interface, C21 to C60
31533	DWDM-SFP10G-80	10GBASE 100GHz DWDM SFP+ 80km, LC Duplex Interface, C21 to C60
14599	DWDM-XFP10G-40	10GBASE 100GHz DWDM XFP 40km, LC Duplex Interface, C21 to C60
14650	DWDM-XFP10G-80	10GBASE 100GHz DWDM XFP 80km, LC Duplex Interface, C21 to C60
35208	QSFP-LR4-40G	40G QSFP+ LR4 1310nm 10km, LC Duplex Interface
35210	QSFP-ER4-40G	40G QSFP+ ER4 1310nm 40km, LC Duplex Interface
35014	CFP2-LR4-100G	100G CFP2 LR4 1310nm 10km, LC Duplex Interface
35192	FS-SOA-G10	10dB Gain 1310nm Semiconductor Optical Amplifier
31366	EDFA-BAO22	20dBm Output C-band 40 Channels 26dB Gain Booster EDFA

Summary

DWDM technology is very necessary to extend Metro Network reach. In this 500Gpbs Metro network, I have introduced very detailed cost-effective solutions. Remember all the indispensable DWDM equipment such as DWDM transceivers, DWDM Mux/Demux, EDFA, etc. For more information, please visit the site about FS.COM Long Haul DWDM Network Solution.

Related articles: How to Extend 40G Connection up to 80 km?
Economically Increase Network Capacity With CWDM Mux/DeMux

Originally published at http://www.fiber-optic-equipment.com

EDFA — the Most Popular Optical Amplifier in Optical Communications

There will be attenuation losses in the fiber when the signals transmit over long distances. To compensate for the attenuation losses, optical amplifier which could restore the optical signal to its original power level without E-O and O-E (electrical to optical and optical to electrical) conversions is needed. Optical amplifier is an important enabling technology for optical communication networks. There are three common optical amplifiers which include erbium-doped fiber amplifier (EDFA), the semiconductor optical amplifier (SOA), and the Raman amplifier. Among them EDFA is most often applied in optical communications.

Definition

EDFA uses a short length of optical fiber doped with the rare-earth element erbium that has the appropriate energy levels in the atomic structures for amplifying optical signal. It’s designed to amplify light at wavelengths around 1550 nm and make wavelengths suffer minimum attenuation in optical fibers. EDFA often uses a 980nm or 1480nm pump laser to inject energy into the doped fiber. The 980nm band has a higher absorption cross-section and is generally used for low-noise performance. The 1480nm band has a lower but broader absorption cross-section and is generally used for high power amplifiers.

Principle of EDFA

The principle of EDFA is shown as the following picture. EDFA usually consists of a length of EDF (erbium-doped fiber), a pump laser, and a component (often known as a WDM coupler) for combining the signal and pump wavelength and an isolator. The pump laser, known as pumping bands, inserts dopants into the silica fiber and makes erbium enter into an excited state. When the weak signals at 1310 nm or 1550 nm travel through the fiber, the lights will stimulate the excited atoms of erbium so that the atoms can release energy in the form of photons. The emitted light photons which have the same wavelength with input signals amplify the optical signals. The signals passing by the fiber will grow stronger and stronger. And the function of the isolator usually placed at the output is to prevent reflections returning from the attached fiber. Because the reflections can disrupt amplifier operation. Thus, EDFA is a high gain amplifier.

Applications

EDFA has many useful functions in telecom systems for fiber communications. For instance, it can boost the power of a data transmitter before entering a long fiber span. It could also be used in front of a data receiver if the arriving signal is weak. What’s more, an EDFA can be used to maintain extended spans of passive transmission fiber. So that the transmission losses through the long distance fiber could be compensated. EDFA is oftern applied in DWDM, CATV, SDH. In addition, an EDFA could be used as the equipment for testing transmission hardware.

Conclusion

In long distance communications, the signals should be amplified to avoid the attenuation losses. There are many kinds of optical amplifiers could be used to amplify the signal but some of them are not very often applied because of certain obvious disadvantages. For example, SOA will add noise to the signal. While EDFA has some interesting properties for fiber optics communications due to its rare-earth element. EDFA is a low-noise amplifier which can simultaneously amplify many data channels at different wavelengths with flat gain, high saturation output power and stable operation. So these advantages make EDFA the most popular in optical communication applications.

Originally published at http://www.china-cable-suppliers.com/