Technical Overview
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The OEM Broadsweeper, tunable, wavelength-swept laser.
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The OEM series of Broadsweepers is a new generation of Superlum's tunable and swept light
sources centered at 790 nm, 840 nm and 930 nm that
are intended for OEM applications.
The optical scheme of the OEM Broadsweeper is based on an external fiber-optic cavity and
a broadband Semiconductor Optical Amplifier (SOA), working as a gain medium. The wide bandwidth of
the SOA modules used, and their high fiber-to-fiber gain allow
wavelength tuning of more than 50 nm at 3 mW of output power.
This power level can be raised to 20 mW with an additional power booster which
is also available.
Specially developed narrow-band Acousto-Optical Tunable Filter (AOTF) is used for wavelength
tuning. All other components comprising the laser cavity are perfectly fitted for broadband
spectral applications. Aberration-free aspherical lenses are used for maximizing the coupling
efficiency to optical fiber and minimizing the insertion losses of the AOTF unit over the
entire tuning range. The filter and its optics are all packaged into one monolithic metal
housing ensuring reliable day-to-day operation without misalignment. Design of the cavity
is "akinteic" with no moving parts inside. The AOTF is actively temperature
controlled for high wavelength stability and accuracy.
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External Cavity of the Broadsweeper-OEM laser. Simplified schematic
(PMF – Polarization Maintaining Fiber, SOA –
Semiconductor Optical Amplifier).
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The external cavity of the laser uses a PANDA-type polarization maintaining (PM) fiber.
This ensures a well-defined state of polarization and its high stability in time and over
the tuning range. Most of fiber-optic components are built by using of the fast-axis-blocking
technology that also guarantees high values of the PER (> 15 dB) at the laser output.
The driving electronics ensures precise, reliable and safe control of the instrument in all
modes of operation. It provides all the necessary laser diode protective measures such as
on-off transients' suppression, over-temperature protection, open-circuit protection and
the laser current limitation by a pre-set safe value. Specially developed fast optical
power control loop allows a flat-top-shaped tuning characteristic (with overall decline not
exceeding 1.2 dB) in all models at all tuning speeds specified. AO cell is
thermally controlled with a tolerance of better than 0.2 °C.
All OEM Broadsweepers provide:
- k-linear wavelength sweeping over the entire tuning range (or in a band of interest)
- high absolute accuracy of a wavelength setting over the entire tuning range in all operating modes including the wavelength sweeping mode
- high stability of the wavelength selected
- high sweep-to-sweep reproducibility of the operating wavelength
The linewidth of the laser emission remains around 0.05 nm over the full
tuning range (FTR) and is not affected by the sweep rate, which can be varied between
1 nm/s and 10000 nm/s.
The output optical power of the Broadsweepers without internal boosters is 3 mW.
It is boosted to 20 mW in the devices with internal optical boosting units.
The following operating modes are available with any standard OEM Broadsweeper:
- Static mode: In this mode, the device operates at any fixed wavelength selected within the FTR (a CW laser diode mode).
- Internal triggering mode: In this mode, the sweep cycle at a pre-set tuning speed (within the tuning speeds specified) is internally initiated. The sweeping range (SR) is selectable within the limits: 5 nm ≤ SR ≤ FTR. The internally-generated synch pulses are accessible via the Remote Control port.
- External triggering mode: In this mode, the sweep cycle at a pre-set tuning speed (within the tuning speeds specified) is internally initiated. The externally-generated synch pulses must be applied to the Remote Control port. The sweeping range (SR) is selectable within the limits: 5 nm ≤ SR ≤ FTR. The device is triggered either by the logical level of a trigger signal (default setting) or by the edge of the signal. The mode of triggering can be changed using the Superlum companion software.
- Single sweep mode: In this mode, a single sweep cycle is initiated each time either by a PC command or by the Superlum companion software which emulates a "pushbutton" on a PC display. Synch pulses generated by the instrument are accessible via the Remote Control port.
The instrument can be locally operated using the top-cover push button. Pushing this button
allows enabling or disabling the laser output only. The device must be remotely pre-configured
to the desired parameters before being locally operated.
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A set of the OEM tunable laser and optical power booster.
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The optical power of the Broadsweeper-OEM laser, which is typically 3 mW,
can be increased up to 20 mW with an optional OEM optical power booster perfectly
fitted to the laser's FTR. Superlum offers a wide selection of OEM power boosters for
the Broadsweeper-OEM series. OEM boosters are compact, easy-to-use, plug-and-play units
(110 × 31 × 190 mm [W ×
H × D]) requiring no adjustments during the lifetime.
Due to the same footprint, the OEM tunable lasers and the boosters can be stacked one on top of
the other provided that sufficient ventilation is ensured.
Both the tunable laser and the power booster can be firmly fixed to a metal bench (or
a flat deck) through the mounting holes in the devices' housings.
Narrow-key FC/APC connectors and mating sleeves are used for all optical connections to
the swept-laser and optical booster. All cables required for quick start and operation are
shipped with the devices.
Remote Control Capability
Each laser of the Broadsweeper-OEM series is equipped with a USB virtual serial port for
setting performance parameters and remote control from an external PC.
With Superlum's companion software, which is supplied with the instrument, the most important
parameters of the device become accessible for control and modification. Using this software,
you get access to:
- Enabling and disabling the laser's output
- Selecting a required mode of operation
- Modifying the instrument parameters including wavelength limits of the tuning range, tuning rate, etc.
- Saving any modifications in the non-volatile memory of the device
- Verifying the device's performance parameters using the self-test feature
For twenty-four-hour-a-day applications, there may be a need to have the instrument periodically
checked to make sure the device is in good operational conditions. To make this procedure as easy
as possible, Superlum offers the self-test function as a part of the Superlum companion software.
The self-test queries all performance parameters required for the device performance evaluation.
The entire process takes only a few seconds to complete. Following this, a list with up-to-date
readings of the operational parameters is generated. It is recommended sending the list to
Superlum for proper interpretation of the obtained data.
There is another way to control the Broadsweeper remotely which is relied on external
TTL pulses applied to the Remote Control port on the back side of the instrument. The device
accepts TTL-compatible pulses (3 – 5 V max.).
Laser Safety Measures
The offered line of optical products includes the units emitting light at power levels of
3 mW / 20 mW (laser / booster) in the near-infrared spectral range,
which is invisible by a human eye. Basing on the values of optical power and the spectral ranges,
these light sources can be classified as Class 3R / 3B laser products (as per
IEC 60825-1 Ed. 3 2014-05). These sources are intended for
integration into the end-user's equipment. These devices do not have the necessary protective
features (such as remote interlock, key operated master control, warning signals,
etc.) required by the Laser Safety standards applicable. Although some of the
features are possible under computer control using the Superlum companion software. It is the
end-user's liability to provide the complete list of the necessary laser safety measures in their
systems where the Superlum light sources are going to be used. Superlum cannot be made liable for
any injury related with the lack of the required laser safety measures in Superlum's
OEM Broadsweepers.
