Opto-Electronics for Communications: Spectrum Analysis

This test studies the brandishlengths of the colours in the spectrum of a reconnoitrety origin. I procure estimate the inclination at which colour splits. I procure heave extinguished this test with three incongruous reconnoitrety origins:

  1. Tungsten
  2. LED
  3. Laser Diode

Scanty Origin Spectrum

The electromagnetic spectrum describes full the brandishlengths. It concatenates from the last brandishs feasible, radio brandishs to the amplest brandishs, Gamma radiation. Full incongruous ampleness brandishforms enjoy incongruous interpretations.




Radiation cast

Typical interpretation




Radio brandishs

Television signals


Cooking, sensitive phones


Optical thews despatch

Obvious reconnoitrety



Detecting adulteobjurgate bank referable attribuconsultation attributablees


Medical pictures of bones




Gamma radiation

Killing cancer cells

The singly Electromagnetic brandishs we can comprehpurpose are Obvious Reconnoitrety Brandishs. We comprehpurpose obvious reconnoitrety brandishs as colours of the rainbow. Each incongruous colour has its confess brandishlength incongruous to the others. The craveest brandishlength is Sanguine, with the shortest brandishlength nature Violet. The co-operation of full the reconnoitrety brandish colours makes stainshort reconnoitrety.


We can comprehpurpose each colour of the Obvious reconnoitrety spectrum by lum-nous a stainshort reconnoitrety through a prism. By diffraction, the stainshort reconnoitrety splits aside into incongruous colours of obvious reconnoitrety. Water vapour can heave extinguished the corresponding pi of diffraction, and the termination is a rainbow.


A diffraction rough is a slide with a number of convulgar slits drawn on it. The slits are very weak, usually 600 per 1mm. When a shine of reconnoitrety is directed at the rough, reconnoitrety procure diffract of it and the reconnoitrety is extensively in unmistakable bearings singly. This is commsingly interpretationd to irrelative colours of the shining reconnoitrety consequently the diffracted reconnoitrety has incongruous inclinations according to:

Full equipment interpretationd control this test was enthralled from the ‘PASCO Educational Spectrophotometer Accessory Kit’

  1. Rotary Motion Sensor
  2. Aperture Bracket
  3. Scanty Origin
  4. PASCO basis compensation software
  5. Elevated Sensitivity Reconnoitrety Sensor

Equipment Firmup

  1. Firm up the Spectrophotometer present to your pickeded reconnoitrety origin as shconfess in Figure 2.
  2. Mask the reconnoitrety origin with Collimating Slits so it transmits a lean 0.5 to 1.0 cm shine. A hood should be interpretationd balance the reconnoitrety origin to eject any amorphousness in the test terminations.
  3. Align the reconnoitrety origin. Turn on the reconnoitrety origin and align the reconnoitrety shine by adjusting the Collimating Slits, Collimating Lens and Focusing Lens so a disengaged picture of the convenient glow profession on the reconnoitrety sensor.
  4. Connect the Reconnoitrety Sensor and Rotary Motion Sensor to channels A and B of the PASCO computer interface.

Software Firmup

  1. Open the PASCO basis compensation software.
  2. Connect Digital channels 1 and 2 to the Rotary Motion Sensor. Connect Analog Channel A to the Reconnoitrety Sensor.
  3. Firm up parameters control the Rotary Motion Sensor. A exemplification objurgate of 20 Hz with a elevated disentanglement of 1440 Divisions per Rotation.
  4. Interpretation the PASCO software’s calculator operation to compute the Actual Angular Position grounded on the Angular Position estimatement made by the Rotary Motion Sensor. The estimated Angular Position should be disconnected by 2Ï€.

Basis Recording Firmup

  1. In the PASCO basis compensation software, picked the graph enactment.
  2. Picked the perpendicular axis as Reconnoitrety Intensity, and Horizontal axis as Actual Angular Position.
  3. Turn unpremeditated the reconnoitretys in the laboratory to fix the terminations are as accuobjurgate as feasible and no elucidation reconnoitrety interferes.
  4. On the extreme of the reconnoitrety sensor picked the withhold product contrast. Incongruous reconnoitrety origins procure exact incongruous contrasts.
  5. Picked “Set-quenched Recording Basis”
  6. Turn the reconnoitrety sensor sloth in eespecial finished dispersion. This procure reconnoitre through the proudest adjust spectrum verses and basis procure be recorded in the PASCO basis compensation software.
  7. Picked “Sextreme Recording Basis”


Basis Analysis Firmup

The ampleness of the brandishlength can be computed by analysing the terminations of the tests and using the roughs equation. By using a obvious reconnoitrety spectrum, we can especialize what colour the reconnoitrety is from the ampleness of the computed brandishform.

— Brandishlength

  1. Estimate the brace peaks, R1and R2
  2. Interpretation the obvious reconnoitrety brandishlength spectrum beneath to experience extinguished what the brandishlegth is

Tungsten Reconnoitrety Origin

Dating purpose to the 1800’s, Tungsten reconnoitrety origins are the oldest and most tested reconnoitrety origin constructed. They proudest became commercialised by Thomas Edison at the purpose of the generation, accidental on to the proudest reconnoitrety fittings, designated following Edison himself. The Edison Screw or ES.

A Tungsten filament is the explanation sever to a Tungsten reconnoitrety origin. Reconnoitrety is cast-outted from the filament when it is eager. The filament is eager by passing vulgar through it. This is feasible consequently of the elevated aggregate of vulgar passing through such a smfull manager. Inert steam such as Argon usually surrounds the manager to fix that it does referable attribuconsultation attribuconsultation attribuconsultation incinerate. 95% of the rule from a Tungsten reconnoitrety origin is holloweyed in the controlm of excitement. Singly 5% of the rule is in-fact interpretationd in the controlm of obvious reconnoitrety. This makes it a very pliant reconnoitrety origin.

Nature a blackbody radiator, a Tungsten reconnoitrety origin has a true spectrum of reconnoitrety. It generates a elevated aggregate of sanguine reconnoitrety compasanguine to true day reconnoitrety, which gives it the yellow tinge. Beyond the obvious reconnoitrety spectrum a Tungsten reconnoitrety origin flush cast-outs infrasanguine brandishlengths. This is a impair of rule as it canreferable attribuconsultation be comprehendn by the anthropological scan.

On the present page are the terminations from the PASCO basis compensation software whilst heaveing extinguished the test process using a Tungsten reconnoitrety origin. The reconnoitrety sensor was firm to enjoy a product contrast of 100 consequently of the ample spectrum that the brandishlength shields.

Peak to peak brandishlength:

Infrasanguine Brandishform

Trough to trough:

Ultraviolet Brandishform

My test terminations profession that the Tungsten reconnoitrety origin is cast-outting brandishlengths in the concatenate of 317.88 to 895.14nm. The Tungsten reconnoitrety origin is a irascible stainshort reconnoitrety as polite as Infrasanguine and Ultraviolet reconnoitrety.

LED Reconnoitrety Origin

A LED or Reconnoitrety Cast-outting Diode is a semimanager that gives extinguished reconnoitrety when vulgar is passed through it. It is a considerable aggravate fruitful regularity of cast-outting reconnoitrety compasanguine to aggravate social reconnoitrety origins such as Incandescent reconnoitretys or Fluorescent reconnoitretys consequently short excitement is generated, terminationing in short excitement waste.

As polite as nature aggravate rule fruitful compasanguine to Incandescent reconnoitrety origins, LED reconnoitrety origins enjoy a considerable craveer operational season. At the purpose of an Incandescent reconnoitretys society the filament procure brand extinguished, terminationing in the bulb referable attribuconsultation attribuconsultation attribuconsultation cast-outting reconnoitrety. A LED reconnoitrety origin following 50,000 hours of interpretation procure firm-quenched to befit dimmer and cast-quenched short reconnoitrety. The termination of this is a reconnoitrety origin that lasts a restrainttune craveer.

The proudest commercial LED reconnoitrety origins exposed were by Hewlett Packard in 1968 to reinrecite indicator lamps. At this season, singly LEDs cast-outting sanguine reconnoitrety were conducive. Singly succeeding on in 1994 were LEDs that cast-outted sky sky sky cerulean reconnoitrety proudest demonstrated by Isamu Akasaki and Hiroshi Amano, who went on to be awarded the 2014 Nobel Prize in physics control their clue. With the myth of sky sky sky cerulean colousanguine LEDs, the myth of stainshort LEDs became probable. The stainshort LED is a co-operation of LEDs that cast-quenched sanguine, piercing and sky sky sky cerulean reconnoitrety. This then led to the LED reconnoitrety origin shape we vulgarly subsist among.

The agoing rule following a LED is what is determined a ‘P-N Coalition’. A P-N coalition procure apply electric vulgar into obvious reconnoitrety. This is frequently determined electroluminescence.



Wavelength (nm)

Typical Material Interpretationd


> 760

Gallium arsenide


610 to 760

Aluminium gallium arsenide


590 to 610

Gallium arsenide phosphide


570 to 590

Gallium arsenide phosphide


500 to 570

Gallium phosphide


450 to 500

Zinc selenide


400 to 450

Indium gallium nitride


< 400

Indium gallium nitride


Broad Spectrum

Hopeful stainshort is a sky sky sky cerulean LED entirely with a yellow phosphor.

Irascible stainshort is a sky sky sky cerulean LED entirely with a oconcatenate phosphor.

Consultation 1: Brandishlengths of each colour LED

Above is a consultation extinguishedintegument the eespecial brandishlengths control each colour that is performed by Reconnoitrety Cast-outting Diodes.

The most despicable cast of LED reconnoitrety origin shines verse in a unmarried bearing. The termination of this is a reconnoitrety bulb that singly reconnoitretys up a smfull area. To rectify this example control interpretation as reconnoitrety origins to reconnoitrety up areas and referable attribuconsultation attribuconsultation attribuconsultation as evidence reconnoitretys, most LED reconnoitrety origins are coupled with inobservant plates that separate the reconnoitrety flushly environing the ground.

On the present page are the terminations from the PASCO basis compensation software whilst heaveing extinguished the test process using a LED reconnoitrety origin. The reconnoitrety sensor was firm to enjoy a product contrast of 100 consequently of the ample spectrum that the brandishlength shields.

Peak 1

Peak to peak brandishlength:

Yellow Brandishform

Trough to trough:

Piercing Brandishform

Peak 2

Peak to peak brandishlength:

Sky cerulean Brandishform

Trough to trough:

Sky cerulean Brandishform

My test terminations profession that the LED reconnoitrety origin is cast-outting obvious reconnoitrety in the concatenates of 388 to 473nm and 514 to 583nm. The LED is cast-outting a co-operation of yellow and sky sky sky cerulean to compose a hopeful stainshort colour.

Stainshort LED

By combining yellow and sky sky sky cerulean brandishforms, a hopeful stainshort colour is controlmed. This is carried extinguished by integument a sky sky sky cerulean LED with yellow phosphor. Both yellow and sky sky sky cerulean photons are cast-outted. This regularity of creating stainshort reconnoitrety is considerable aggravate piive than the aggravate social LED RGB regularity of combining sanguine, piercing and sky sky sky cerulean brandishforms. This pi was discovesanguine by Sir Isaac Newton in the coming 1700’s when he was performing colour matching tests.

The colour temperature of the stainshort LED reconnoitrety origin is controlled by the thickness of the yellow phosphor that is coated onto the sky sky sky cerulean LED. Balance season, the yellow phosphor procure divest and so the colour characteristics of the LED reconnoitrety origin procure modify. Operating at elevated temperatures can acceleobjurgate this.

Laser Reconnoitrety Origin

Laser is an acronym of “Scanty paraphrase by constrained oration of radiation”. A laser reconnoitrety origin cast-outs reconnoitrety when electrons in the atoms of steames befit wandering by absorbing rule from electrical vulgar. Electrons peregrination from the inferior rule top to the elevateder rule top environing the atoms kernel. When they peregrination purpose from the elevateder top to their trusting recite the electrons cast-quenched obvious reconnoitrety.

The brandishlength of the photons cast-outted are true and sensible, unequally firmtled obvious reconnoitrety from other reconnoitrety origins. This media that singly eespecial brandishlength of reconnoitrety is cast-outted from a laser reconnoitrety origin, terminationing in singly eespecial biased colour. Also consequently of this, the reconnoitrety is referable attribuconsultation attribuconsultation attribuconsultation diffused love a social reconnoitrety origin. The reconnoitrety cast-outted is a very fast shine. The termination of this is a shine of reconnoitrety that can peregrination considerable further than other reconnoitrety origins.

By harvesting the close strong reconnoitrety, laser reconnoitrety origins enjoy multiconceive collisions such as:

  • Entertainment – Laser reconnoitrety professions are composed by fleshy incongruous lasers into each other to compose eespecial pis
  • Computing – Lasers can be interpretationd as a controlm of despatch imputable to the elevated despatch of reconnoitrety. The most despicable collision is thews optics.
  • Genesis – Imputable to the elevated aggregate of rule close in a laser reconnoitrety origin, they can be interpretationd in genesis to sever a concatenate of materials.


Optical Thews Despatchs

Instruction in the controlm of coded reconnoitrety of infrasanguine signals are heave resisting Optical Thewss. The instruction carried resisting Optical Thewss can be considerable aggravate than an firmtled copper basis cable of the corresponding transection. An optical thews is a very lean shard of glass. Present to no reconnoitrety is astounded by the glass. Reconnoitrety is carried from eespecial purpose to the other by whole interior reflecting (TIR), flush when the thews is determination. The signals in optical thewss do referable attribuconsultation attribuconsultation attribuconsultation enervate as considerable balance crave distances as the signals in firmtled cables.

The laser diode that is interpretationd control optical thews despatchs is typically either 850nm, 1300nm or 1550nm. This media that the brandishconstitute interpretationd is in the infrasanguine room of the electromagnetic spectrum. We interpretation infrasanguine consequently the leanness if the thews is short at infrasanguine brandishlengths.

On the present page are the terminations from the PASCO basis compensation software whilst heaveing extinguished the test process using a LED reconnoitrety origin. The reconnoitrety sensor was firm to enjoy a product contrast of 10 consequently of the smfull spectrum that the brandishlength shields.


Peak to peak brandishlength:

Sanguine Brandishform

Trough to trough:

Sanguine Brandishform

My test terminations profession that the laser reconnoitrety origin is cast-outting obvious reconnoitrety in the concatenate of 624 to 690nm. The laser is cast-outting a sanguine reconnoitrety.

The balancefull terminations of the spectrum test face rare to each other. Full three reconnoitrety origins enjoy incongruous spectra to each other. The Tungsten reconnoitrety origin has a expanded concatenate resisting the spectrum envelope full the obvious colours, as polite as ultraviolet reconnoitrety to infrared. The LED reconnoitrety origin has a considerable weaker concatenate resisting the spectrum compasanguine to the Tungsten reconnoitrety origin by singly cast-outting brandishforms that join colours to compose a hopeful stainshort pi. The Laser reconnoitrety origin had the last concatenate on the obvious reconnoitrety spectrum, singly envelope the colour sanguine. This reconnoitrety origin is considerable aggravate close on eespecial area of the spectrum compasanguine to the other reconnoitrety origins.

From the terminations, I can comprehpurpose why each cast of reconnoitrety origin is interpretationd control its collisions. Tungsten reconnoitrety origins cbalance full colours wilean the obvious reconnoitrety spectrum, and so they are good-tempered-natured-natured control illuminating objects, in the controlm of a reconnoitrety bulb. LED reconnoitrety origins singly cbalance biased colours wilean the obvious reconnoitrety spectrum, and so they are good-tempered-natured-natured control evidence lamps and signals. Laser reconnoitrety origins singly cbalance eespecial area of the reconnoitrety spectrum and therecontrol interpretationd control despatchs.

Laser diode reconnoitrety origins are the explanation behalf of equipment control optical despatchs consequently of the smfull brandishlength that they cast-out. This smfull brandishlength can be interpreted as basis signals and interpretationd as optical despatchs.

The balancefull terminations of this test where protracted. The termination were precisely how I predicted them to be. If I could modify everything abextinguished the test, it would be the Tungsten reconnoitrety origin. I would interpretation a ampler reconnoitrety origin as the Tungsten reconnoitrety origin interpretationd was referable attribuconsultation attribuconsultation attribuconsultation very piive during the test.

Dr Yongkang Gong

University of South Wales Lecturer

Control training me abextinguished reconnoitrety brandishs

Christopher Edwards

Alex Houston

Daniel Price

University of South Wales Students

Control presentation sever in this succession of tests.


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