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## Pre-FEC BER corresponding to Q.

• BER and Q can be calculated from one another according to the following relationship:

• Or, in Excel: dBQ = 20*LOG10(-NORMSINV(BER))
• dBQ = 20Log(Q)

## Post-FEC BER/Q

• Post-FEC BER of <1e-15 essentially means no post-FEC errors
• This is equiva…

### Quick note on Physical Coding Sublayer (PCS) error in Optical System

What is PCS ?

The Physical Coding Sublayer (PCS) is a networking protocol sublayer in the  Ethernet standards. This layer resides at the top of the physical layer (PHY) which provides an interface between the Physical Medium Attachment (PMA) sublayer and the media-independent interface (MII). Thi…

### Understanding Optical Return Loss (ORL) in Optical Fiber system

Optical fiber communication professionals might have heard  about ORL (Optical Return Loss ) during design and operation on an Optical Fiber Network.Intend of this article is to share the information on this topic which could help optical fiber  engineers and professionals understanding the concept …

### Automation in Optical Networking:If you are reading this you can do this !!!

Automation in Optical Networking

If you are reading this you can do this!!!

Google , Stackoverflow and your little efforts will do it.No worries!!!

### Calculating Channel Capacity for DWDM links

The maximum data rate (maximum cha…

### Calculating Transponder bandwidth

Transponder bandwidth is the product of Modulation , Baud Rate and the Polarisation.

BW=Modulation x Baud x Polarisation

Following table will give an idea for various bit rates:-

Ex:

Modulation = 2 (bits/s/Hz)

Baud Rate = 32G

Polarisation= 2

BW= 2 x 32 x 2 =128Gbps

# Introduction

The 980nm pump needs three energy level for radiation while 1480nm pumps can excite the ions directly to the metastable level .

(a) Energy level scheme of ground and first two excited states of Er ions in a silica matrix. The sublevel splitting and the lengths of arrows repre…

### Techniques/technologies to mitigate compensation in long haul submarine optical networks

Map of transmission impairments in long-haul submarine systems and some techniques/technologies for their mitigation or compensation.

### Spectral Hole Burning (SHB) phenomenon in Optical Networks

Spectral Hole Burning (SHB)

Spectral hole burning (SHB) is a major limitation of amplified WDM systems with high channel count. The main reason lies in the fact that there is no possibility of compensating for this effect.

• Due to the inhomogeneous portion of the linewidth broadening of the dopan…

### Difference between EDFAs requirements for Terrestrial(Land) Systems and Submarine Systems.

Compared with requirements for EDFAs for terrestrial applications and for Submarine applications, there are major important differences making the two types of amplifiers definitely two different components.

 Terrestrial(Land) system Submarine System •Relia…

### Temperature dependency of EDFA Gain for various channels

Here the results are after evaluating the effect of a thermal variation on the output tilt. In this particular set-up the amplifier is kept at room temperature (25 °C) and only the active fiber spool undergo a thermal cycle. Temperature of the EDFA is varied from 0 °C to 65 °C and the amplifier gain…

### Simplifying what and why of Raman Amplifier.

It's always a wondering situation when we discuss Raman Amplifier;its benefits , requirement and application.I have tried to make it simpler to understand here.

Hope it will help the readers.

Introduction

• The Raman amplifier is typically much more costly and has less gain than an Erbi…

### How Layer 0(zero) is so efficient with "Latency" -One of the key parameter for Operator.

Layer 0(zero) merely introduces any latency to the network.

• It's mostly the electronics that imparts latency in the network.
• The more we play with bit streams/signals ;more will be the latency.
• Most of the latency optimization happens in layer 1-3.

Future Transport Network R…

### Optical Fiber Link Design requirements

The optical link design essentially is putting the various optical components, which we discussed earlier, so that information can be transmitted satisfactorily. The satisfactoriness of the transmission can be defined in terms of some characteristic parameters.

The user generally specifies the dis…

# How and where do we get pre and post FEC BER

The first thing to note is that for each frame there are two sets of 20 parity bits. One set is associated with the end to end post FEC BER. The other is used to measure the span by span raw BER. The points at which these parity bits are terminated are…

### MAXIMUM NUMBER OF ERBIUM-DOPED FIBER AMPLIFIERS IN A DWDM LINK

The maximum number of erbium-doped fiber amplifiers (EDFAs) in a fiber chain is about four to  six.

Explanation

The rule is based on the following rationales:

1. About 80 km exists between each in-line EDFA, because this is the approximate distance at which the signal needs to be ampli…

### Why is it preferable to put attenuator/pad at the Receive end of Optical Module?

Few analogies proving the subject:-

• If the distance is to short and the attenuator is too close to the transmitter, the reflected light off the attenuator will be directed back towards the Tx laser. Which will also blow your transmitter.so we place it at Rx.

• Also keeping…
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