Operating The Int-Mzi-Xxx; General Principle Of Operation; Optical Input And Output, Fiber Network - THORLABS INT-MZI Series Operation Manual

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Operating the INT-MZI-xxx

3.1 General Principle of Operation

The Thorlabs INT-MZI-xxx series MZI Clock Box is a subassembly to be used in swept
source OCT systems and other applications. It contains a fusion coupler network and ultra-
low noise, high-speed transimpedance amplifiers with low output impedance to provide a
Power Monitor signal as well as a k-Clock signal to monitor both the output power and
wavelength of a swept laser source. The used couplers are optimized for flat wavelength
response and very low PDCR (polarization dependant coupling ratio change) to make the
Power Monitor signal nearly independent to input polarization changes.
The INT-MZI-xxx series is powered by the included external mains power supply (12 V,
250 mA) via a PICO M8 power connector.
Figure 2 shows the functional block diagram of the INT-MZI-xxx series MZI Clock Box.
INPUT INPUT
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OUTPUT OUTPUT
Figure 2: Functional block diagram of the INT-MZI-xxx series

3.2 Optical Input and Output, Fiber Network

The INT-MZI-xxx MZI Clock Box subassembly is equipped with ~50 cm long INPUT and
OUTPUT pigtails with FC/APC connectors to be connected to your application. Model INT-
MZI-1300 uses Corning SMF28
HP TM single mode fiber.
NOTE
FC/APC connectors are used for INPUT and OUTPUT pigtails!
Saturation of the electrical outputs may occur at optical input power > 50 mW. The optical
damage threshold is 250 mW. Exceeding this value may permanently destroy
detectors!
An internally fiber network is used to tap ~5% of the input light to generate Power Monitor
and k-Clock signals. The remaining light is transmitted to the Output pigtail. Insertion loss
(Input to Output) is less than 1 dB (model INT-MZI-1300), including connector losses. This
tap coupler is designed for nearly flat transmission wavelength response (see Figure 3).
The sophisticated design of the 50/50 fusion coupler provides a Power Monitor output
signal with flat wavelength response, which is nearly insensitive to input polarization
changes. Figure 4 shows the typical spectral behavior of the INT-MZI-1300 measured from
Input to Power Monitor output port.
© 2018 Thorlabs
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MZI section MZI section
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INT-MZI-xxx INT-MZI-xxx
TM single mode fiber. Model INT-MZI-850 uses Nufern 780-
Operating the INT-MZI-xxx 7
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MZI Output MZI Output
Power Monitor Power Monitor
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