Introduction to Optisystem

And practical optical systems

Simulations and design by

Introduction to Optisystem :

Optisystem is a professional modern simulation software

produced by Optiwave Company which made great efforts in the

interests of optical communications system and practical

applications of optical networks, Fig. 4-1 shows Optiwave and

Optisystem logos.

Fig. 4-1, Optiwave and Optisystem logos

What kinds of Applications can be done?

OptiSystem gives us the ability to simulate/design:

• Next Generation optical networks.

• Current optical networks.

• SONET/SDH ring networks.

• Amplifiers, receivers, transmitters.

What about Analysis Tools provided?

OptiSystem enables users to simulate and get results via great

tools provided such as:

• Eye diagrams, BER, Q-Factor, and Signal chirp.

• Polarization state, Constellation diagrams.

• Signal power, gain, noise figure, OSNR.

• Data monitors, report generation, and more!

Getting Started with Optisystem Environment :

After Optisystem being installed, we can do all benefits of

simulations and designs, let's start here!

• To start the program go:

Start menu� Programs� Optiwave Software� Optisystem 7�

Optisystem, as shown in Fig. 4-2.

Fig. 4-2, Path toward Optisystem

When Optisystem opens, the main window would be as shown

in Fig. 4-3.

Fig. 4-3, main window of Optisystem

Basic optical components and systems:

Simulations and designs in Optisystem in mainly depends on

block diagrams, we place all needed blocks of sources,

channels, multiplexers, scopes…etc then run the simulation to

get results.

Example 4-1: simple optical transmitter system:

Create a new design work sheet and place the following

components from the default library directory to the left of the

workspace.

• Continuous Wave (CW) Laser, a great

commonly used optical source.

• Optical Power Meter, a scope used to

estimate the power of an optical signal.

• Optical Spectrum Analyzer, an optical

analyzer to show where most energy of an optical signal

exists, i.e., the fundamental frequencies region.

• Optical Time Domain Visualizer, a

scope to show us the optical signal in normal time

domain.

• Optical Fiber, The Optical Channel.

Make the needed Connections for the blocks to get our system

and edit needed blocks parameters as shown in Fig. 4-4.

Fig. 4-4, Simple Optical Transmitter system

Block diagram of Example 4-1

To Edit any block parameters, double click on the block the

make changes in need as following:

• CW Laser: set Frequency to 193.1 THz and the source

Power to 1 mW, as shown in Fig. 4-5.

Fig. 4-5, editing CW Laser Parameters

• Optical Fiber: set Length to 20 km and Attenuation to

0.1 db/km, as shown in Fig. 4-6.

Fig. 4-6, editing Optical Fiber Channel Parameters

Now, let's run simulation and calculation results by clicking on

the icon to perform simulation.

• Note: Simulation with Optisystem may take several

minutes in large systems and designs.

After calculations are finished, we can click on scopes to view

results, for example:

• To view the power used by the CW Laser source, double

click on the Optical Power Meter related to it, as shown in

Fig. 4-7.

Fig. 4-7, CW Laser Power Meter

• Same way to view power at the end of the channel, look

Fig. 4-8.

Fig. 4-8, Optical Power Meter at the end

Of the 20 km Fiber Channel.

• Now let's see the Optical Spectrum Analyzer to

investigate fundamental frequency of transmitted signal,

look Fig. 4-9.

Fig. 4-9, Spectrum Analyzer Scope Screen

� Notes:

• Spectrum Analyzer results are shown versus the

Wavelength which more commonly used instead of

Frequency in Optical Communications.

• It's known that Wavelength of Light is related to

Frequency as following:

f

c=λ where,

λ: wavelength

c: speed of light ≈ 300000 km/s. f: frequency.

Thus in our case we have:

553.1101.193

103

12

8

≈×

×≈=

f

cλ µM

Example 4-2: 16-QAM Modulation system:

Create a new design work sheet and build in the following

system shown in Fig. 4-10 by placing components directly from

the library directory to the left of the workspace.

Fig. 4-10, Design for Example 4-2

New blocks used are:

• Pseudo-Random Bit Sequence

Generator, Used to generate bits sequence randomly.

• QAM Pulse Generator, Used to

generate M-Array QAM Pluses/Symbols.

• Electrical Constellation

Visualizer, a scope to scatter-plot the symbols in

Constellation diagram.

• Electrical Adder, used to perform the

summation of 2 electrical signals.

• Electrical Phase Shift, used to

delay/shift the phase of an electrical signal.

• Noise Source, simulates the noise at

specific noise power.

• Mach-Zehnder Modulator, to

modulate the optical signal according to the electrical

pulses.

To Edit any block parameters, double click on the block the

make changes in need as following:

• QAM Pulse Generator: set the bits per symbol to 4 to

get a 16-QAM system and the duty cycle to 1(100%) as

shown in Fig. 4-11.

Fig. 4-11, Parameters for QAM Pulse Generator

• Electrical Phase Shift: set the Phase shift to 90 deg,

which will be used to prepare the imaginary part of the

QAM scheme, look Fig. 4-12.

Fig. 4-12, Parameters for Electrical Phase Shift

• Noise Source: set the Noise Power to be -80 dBm as

shown in Fig. 4-13.

Fig. 4-13, Parameters for the Noise Source

Now, let's run simulation and calculation results by clicking on

the icon to perform simulation.

After calculations are finished, we can click on scopes to view

results, for example:

• To view the Constellation of the 16-QAM, double click on

the Electrical Constellation Visualizer, look Fig. 4-14.

Fig. 4-14, Constellation of 16-QAM

• To view the optical signal transmitted after modulation,

double click on the Time Domain Optical Visualizer, look

Fig. 4-15.

Fig. 4-15, Time Domain Optical signal

Notice the noise effect!

� Notes:

• Optisystem provides abilities to design many other

common modulation systems such as PSK, PAM,

FSK and son on using same methods.

• By applying the number of bits needed for each

symbol we then apply the system to be Binary, 4,

8, 16, 64, 128…-QAM.

• It's a good practice to set noise power to practical

values, thus our design be more realistic.

Example 4-3: WDM Optical System with 4 Channels:

Create a new design work sheet and build in the following

system shown in Fig. 4-16(a, b and c) by placing components

directly from the library directory to the left of the workspace.

Note: The Design is wide to show in a single Fig. so we have

portioned it into 3 graphs as shown in Fig. 4-16(a, b and c).

Fig. 4-16-a, Design of Example 4-3,

These blocks are the most left

in the Design work sheet

Fig. 4-16-b, Design of Example 4-3,

These blocks are the middle

in the Design work sheet

Fig. 4-16-c, Design of Example 4-3,

These blocks are the most right

in the Design work sheet

New important blocks used are:

• WDM Mux 4x1, an optical

multiplexer of 4 channels input being multiplexed into 1

output channel.

• EDFA, the common and

known Erbium Doped Fiber Amplifier.

• WDM DeMux 1x4, and optical

demultiplexer with 4 output channels being recovered

from 1 input channel.

• BER Analyzer, Bit Error Rate

Analyzer, provides BER estimations with graphs.

• Photodetector PIN, an optical photo

detector receiver, converts light into corresponding

electrical signal.

• Low Pass Gaussian Filter, a

low pass electrical filter with Gaussian response.

• RZ Pulse Generator, a return to zero

pulses generator from bits sequence.

• WDM Analyzer, a tool helps in

WDM analyzing.

Now, let's run simulation and calculation results by clicking on

the icon to perform simulation. Then we can click on scopes to view results, for example:

• To view the optical spectrum of the multiplexed

channels, double click on the optical spectrum, look

Fig. 4-17 below.

Fig. 4-17, Optical spectrum of the 4 multiplexed channels

• The WDM Analyzer can give us some useful

information about the multiplexed channels and how

much each channel is affected by noise, see Fig. 4-18.

Fig. 4-18, WDM Analyzer Window

• The other important estimation is the BER information

so make double click on the BER Analyzer block and

mark the Shoe Eye Diagram, Fig. 4-19.

Fig. 4-19, Details about BER and Eye Diagram

The Analyzer as well shows the Eye Diagram as shown in

Fig. 4-20 below.

Fig. 4-20, Eye Diagram shown by BER Analyzer