ECE 183 2012 Lab #3 Tunable laser diode (Agility)

B. Spectral Characteristics of Multimode Fabry-Perot LD.
In this part of the experiment you will be using multimode Fabry-Perot LD from Chorum
Technology, model LDLS-02.
- Using the fiber patch-cord connect LD output with spectrum analyzer input.
- Observe the output spectrum of Multimode LD on the OSA.
Describe what you see.
- Measure the spacing between successive peaks.
- Find the modal frequency spacing ∆ν. (Remember that ∆λ =1nm corresponds ∆ν =
125GHz for central wavelength of 1550nm)
- Calculate the length of the laser resonator. Refractive index of the laser material n = 3.7.
C1. Spectral Characteristics of DFB LD.
In this part of the lab you will be using a DFB Laser Diode, model S3FC1550 from
ThorLabs.
Switch-on Procedure of the DFB Laser Diode:
• Switch-on the line power of the laser diode driver.
• Push “Enable” button to activate the laser light emission.
• Set the temperature controller to 20ºC.
• Set the power output to 1mW.
- Using the fiber patch-cord connect LD output to OSA.
- Set the spectrum analyzer center wavelength to 1550 nm and the span to 5 nm.
You should easily observe a peak in the spectrum with no substantial noise for +/- 1 nm
or so around the peak. At this point center the peak and change the span to 1 nm.
- Measure the center wavelength and bandwidth of the output spectrum on -3db level.
C2. Temperature tuning of DFB laser.
- Set the laser power to 1mW and initial temperature to 15ºC.
- Observe the spectrum. Adjust the central wavelength to move the peak to the left side of
the OSA display.
- Measure the peak wavelength.
- Change LD temperature by 5ºC and observe shifting of the peak.
Note that temperature controller need some time to settle to the new value.
- Continue changing the temperature with 5ºC step until it reaches 40ºC and record the
peak wavelengths.
- Plot λ vs. T. Describe the temperature dependence of the output spectrum. Does the
output wavelength tune smoothly with temperature? What is the wavelength tuning range
of this DFB laser?
7