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Writing your thesis

March 2nd 2011Faisal Rafiq Mahamd Adikan

Department of Electrical Engineering

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Outline

Before you begin

Good practices

Bad practices

 Assessment

Questions and Answers

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Before you begin

One writer – many readers

Burden on writer to communicate efficiently

Make a calculated judgment on how basic/advanced the thesiswill be

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Before you begin

Do the homework

Pick up a good thesis and see how things are done

Masters or PhD thesis should be OK

Start early

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Before you begin

Tell a story

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Before you begin

No limit to number of chapters, and how long a chaptershould be

Should fit into a nicely told story

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Good practices

 Abstract : should be quantitative where possible

Describe results obtained

Do not put anything introductory in nature. Perhaps a sentenceor two would do

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Good practices

This thesis describes a series of experimental studies concerning waveguide structures based on the direct UV and direct grating

writing fabrication techniques. The latter approach allows simultaneous definition of waveguide structures and Bragg gratings.

The first result of this work describes the fabrication and characterisation of small angle X-couplers that exhibit low polarisation

and wavelength dependence. Maximum and minimum coupling ratios of 95% (±0.8%) and 1.9% (±1%) respectively with typical

excess loss of 1.0dB (±0.5dB) were recorded. Device modelling using Beam Propagation Method (BPM) and an analytical model

showed good agreement with experimental results over a broad crossing angle and wavelength range.

By introducing refractive index asymmetry in 2° X-couplers, it was possible to tune the response to give a 50:50 coupling ratio.

Multiple UV exposure experiments investigated the 'proximity effect' and provided further proof of the ability of UV writing to

produce raised waist index X-couplers.

 A first order Bragg grating electrically tunable via liquid crystal index modification with a maximum tunability of 141 GHz at

1562nm (TM polarised) and 114 GHZ at 1561.8nm (TE polarised) using electro-patterned ITO coated glass electrodes is also

presented. The 141GHz tuning range effectively covers up to five 25 GHz WDM channel spacing and was achieved with 170Vpp

sinusoidal 1 kHz supply voltage. Hysteretic behaviour of the tuning curves was observed and is believed to be related to thedynamics of the disclination line formed along the waveguide axis with increase or decrease in supply voltage.

Finally, a description of the successful demonstration of UV-written single channels, y-splitters, and Bragg gratings into a novel

flat fibre substrate is provided. Utilising a series of Bragg gratings enabled assessment of the core layer uniformity and

birefringence.

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Good practices

Introduction : should introduce

The setting - overview

What is the problem you wish to solve

Objective(s) – those you need to fulfill to solve the above

problems

Thesis structure

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Good practices

The chapter previously known as ‘Literature Review’  

There should NOT be any chapters called Literature Review

Should be ‘Introduction to ..’, or ‘Flat Fibres: A Brief Overview’  

Should be scientifically thick

Show that you have read a lot

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Good practices

The chapter previously known as ‘Literature Review’  

Use tables

Material 

(typical refractive

index )+

 

Index

contrast n  Waveguide fabrication 

Typical propagation

loss Refs. 

SiO2:Si

(SiO2  1.4 - 1.5,

Si  3.3 – 3.5)

5 - 7 (x 10-3)i. photolithography & etching

i i. direct UV writing 0.03 - 0.1dB/cm [4-6]

Lithium niobate

(LiNbO3  2.2) 10-3 

i. zinc/titanium in-diffusion

ii. proton exchange0.1 – 1dB/cm [7]

Indium phosphide

(InP  3.3)Up to 0.1 i. photolithography & etching > 1dB/cm [3]

Polymers

(n   1.3 – 1.6)Up to 10-3 

i. photolithography & etching

ii. laser ablation

iii. moulding/embossing

0.01dB/cm (= 840nm)

0.1dB/cm ( = 1550nm)[8]

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Good practices

The chapter previously known as ‘Literature Review’  

Use flow diagrams (to indicate technology placing)

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Good practices

The chapter previously known as ‘Literature Review’  

Use diagrams

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Good practices

Experimental configurations

Use diagrams and images : bring readers there

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Good practices

To indicate dynamic behaviors

Use composite graphs

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Good practices

To show dynamic behaviors

Use composite graphs

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 Assessment

How your thesis will be assessed

Limit to 50-pages long (including diagrams, and tables)

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Questions?