In this paper, we demonstrate the performance of self-fabricated passive fiber components in a laser and amplifiers setups operating at ~1.55 μm wavelength. Three different types of power combiners and one mode field adaptor were fabricated using three-electrode Large Diameter Splicer System (LDS System). Application of pump and signal power combiners in two configurations is presented, including (5+1)x1-SM (i.e. with single mode signal fibers) and (6+1)x1-LMA (with large mode area signal fibers). We also demonstrate pump power combiner in 7x1 configuration with single mode output fiber and mode filed adaptor which connects single mode fiber with large mode area type fiber. All those components were successfully applied in two high-power systems, a three-stage amplifier MOPA setup and a high-power amplifier with medium-power signal source.
In this work, we demonstrate a high-pulse energy, fiber-based chirped pulse amplification (CPA) setup utilizing Er- and Er/Yb-doped fibers, operating at 1555 nm central wavelength. The integrated pulse-picker allows to reduce the repetition frequency down to the kHz-range, which enables generation of sub-picosecond pulses with energies above 2 μJ and pulse peak power exceeding 1 MW. The system utilizes an Er/Yb co-doped large mode area fiber in the final amplification stage. Thanks to the used mode-field adaptors, the setup is almost fully fiberized, except the bulk grating pulse compressor.
In this work, we would like to demonstrate our results on performing (6+1)x1 tapered fiber bundle combiners using a trielectrode fiber splicing system. In our combiners we have used 9/80 μm (core/clad) diameter fibers as single-mode signal input ports. Using this fiber, instead of a conventional 9/125 μm single-mode fiber allowed us to reduce the taper ratio and therefore significantly increase the signal transmission. We have also performed power combiner which is based on the LMA fibers: input signal fiber 20/125μm and passive double clad fiber 25/300 μm at the output.
In this paper we present a device - fiber based coherent light source operating at 1550 nm wavelength and 5 W of the
output power. It is made completely of the fiber elements without any bulk optics therefore it is stable and resistant to the
environmental conditions. The main idea was to use so called MOPA (Master Oscillator Power Amplifier) configuration
to obtain universal design. Thus the device can be easily configured to work in couple different operation regimes.
This paper presents the analysis of the impact of selected process parameters on the resulting laser color marking. The
study was conducted for AISI 304 multipurpose stainless steel using a commercially available industrial fiber laser. It
was determined how various process parameters, such as laser power, scanning speed of the laser beam, temperature of
the material, location of the sample relative to the focal plane, affect the repeatability of the colors obtained. For
objective assessment of color changes, an optical spectrometer and the CIE color difference parameter ΔEab
* were used.
For the last few years we were elaborating the laser-fiber vibrometer working at 1550 nm. Our main stress was directed towards different aspects of research: analysis of scattered light, efficient photodetection, optimization of the fiber-free space interfaces and signal processing. As a consequence we proposed the idea of a multichannel fiber vibrometer based on well developed telecommunication technique – Wavelength Division Multiplexing (WDM). One of the most important parts of a fiber-laser vibrometer is demodulation electronic section. The distortion, nonlinearity, offset and added noise of measured signal come from electronic circuits and they have direct influence on finale measuring results. We present the results of finished project “Developing novel laser-fiber monitoring technologies to prevent environmental hazards from vibrating objects” where we have constructed a 4-channel WDM laser-fiber vibrometer.
A new design of an erbium-ytterbium doped fiber amplifier is demonstrated. The amplifier contains a wavelength-tuned
loop resonator for the 1 μm signal. The amplified spontaneous emission (ASE) from Yb ions is used to stimulate a laser
emission at several wavelengths from the 1 μm band in the 1550 nm amplifier. The wavelength of this lasing is selected
by introducing a spectral filter. The results show, that the efficiency of the amplifier at nominal 1550 nm wavelength can
be increased by introducing a feedback loop with 1040 nm and 1050 nm filters. This loop also protects the Er-Yb
amplifier from parasitic lasing and allows output power scaling without risk of self-pulsing at 1 μm.
In this work we present a new design of Er/Yb co-doped fiber amplifier with controlled amplified spontaneous emission
(ASE) at 1 μm. The Yb-ASE is controlled by stimulating a laser emission at 1064 nm in the amplifier, by providing
a positive 1 μm signal feedback loop. The results were discussed and compared to a conventional amplifier setup without
1 μm ASE control. We have shown, that applying a 1064 nm signal loop in an Er/Yb amplifier can increase the output
power at 1550 nm and provide stable operation without parasitic lasing at 1 μm.
In this work we present a high-power laser source developed in Master Oscillator Power Amplifier (MOPA)
configuration. Presented MOPA source consists of three amplifying stages: pre-amplifier based on erbium-doped fiber,
medium-power stage based on double-clad Er/Yb co-doped fiber and the power stage, based on Er/Yb co-doped doubleclad
LMA fiber. Whole system is set up in All-In-Fiber technique, without any bulk, free-space optical elements. It
provides over 20W of output power in the eye-safe 1550 nm band.
The WDM fiber transmission technique was used to measure vibration parameters of four points of a vibrating object.
The 4-independent laser diodes form a WDM system according to the rule 'one wavelength-one analyzed point'.
Keywords: laser Doppler vibrometry, fibre vibrometry, heterodyne detection, multichannel vibrometry.
The paper describes stepped frequency continuous wave (SFCW) ground penetrating radar (GPR), where signal's
frequency is discretely increased in N linear steps, each separated by a fixed ▵f increment from the previous one. SFCW radar determines distance from phase shift in a reflected signal, by constructing synthetic range profile in spatial time
domain using the IFFT. Each quadrature sample is termed a range bin, as it represents the signal from a range window
of length cτ/2, where τ is duration of single frequency segment. IFFT of those data samples resolves the range bin in into fine range bins of c/2N▵f width, thus creating the synthetic range profile in a GPR - a time domain approximation of the frequency response of a combination of the medium through which electromagnetic waves propagates (soil) and
any targets or dielectric interfaces (water, air, other types of soil) present in the beam width of the radar. In the paper,
certain practical measurements done by a monostatic SFCW GPR were presented. Due to complex nature of signal
source, E5062A VNA made by Agilent was used as a signal generator, allowing number of frequency steps N to go as
high as 1601, with generated frequency ranging from 300kHz to 3 GHz.
In recent years we have observed growing interest in mode-locked fiber lasers. Development of erbium doped fiber
(EDF) amplifiers and WDM technique made 3rd telecommunication window extremely interesting region for ultrafast
optics. The main advantages of fiber lasers i.e. narrow linewidth and wide gain bandwidth make them very attractive
sources in various applications. In this paper we present an actively mode-locked erbium doped fiber ring laser. Modelocking
is obtained using an acousto-optic modulator (AOM) coupled into the laser cavity. The impact of different
parameters (e.g. light polarization, modulation frequency) is investigated. We study mechanisms of controlling the
wavelength of the laser.
The multichannel WDM (Wavelength Division Multiplexing) technique inspired the concept of vibration measurements
for many points of a vibrating object. The N-independent WDM separated 15XX nm fibre coupled laser diodes (used for
optical fibre telecommunication) form coherent system of sources for multipoint measurement of vibrations according to
the rule one wavelength - one point. The scattered light from the object coupled into the fibre, filtered coherently, after
special signal processing, allows analysing amplitudes and phases of many vibrating points in real time. Some
experiments and results of such system will be demonstrated.
Microwave frequency discriminator (MFD) is a device, which is used to generate signal carrying information about
frequency of input signal. Depending on type of subassemblies, which were used in examined MFD, its parameters will
change. Developed simulator BP-PK-V2.0 is able to measure frequency of virtual or obtained from measurement by
other microwave devices signals. Its most important feature is, that the program enables its user to test parameters of
discriminator created from certain subassemblies without manufacturing physical device and, when the results are not
satisfactory, remodeling its structure with one or more elements. Tests will end when expected performance is achieved
and only then should simulated MFD be implemented in PCB. Two types of visualization, in which described simulator
is equipped with, enable to determine properties of two methods of estimating measured value: continuous method
(with high resolution) and discrete method, in which information precision is limited to subrange with finite width.
There is a necessity of development a stable and calibrated laser sources for modern WDM telecommunication systems. Additionally simultaneous oscillations of many wavelength are required for testing and diagnostic of such systems. This regime of operation is possible in Frequency Shifted Feedback Lasers (FSFL). The multiwavelength erbium doped fiber laser is presented in this paper. The acoustooptical Bragg frequency shifter (AOFS) in the laser cavity ensures stable and multi-frequency operation by preventing steady-state regime. The wavelengths forced by Fabry-Perot filter cover part of third window (1550 nm).
The bulk acoustooptic Bragg modulator shifting light frequency at 105MHz, adapted at the 1550 nm bandpass and coupled into single-mode telecommunication fiber is presented. It was used in the experiment of self-heterodyning measurements of semiconductor lasers spectral linewidth.
We presented the next step of our research connected with development of the vibrometry/velocimetry based on fiber into free space radiation and heterodyne detection of scattered light. Some experimental configurations utilizing erbium doped fiber amplifier (EDFA) are presented. We propose two solutions of optical interface between the fiber system and an object.
A pulsed excitation of the laser plasma in gas lasers creates an acoustic wave in the laser reservoir. It changes thermodynamic parameters of the laser plasma in the laser cavity like pressure, and temperature, as well, and consequently it changes the density of the laser plasma, or, in other words, the refractive index of the laser medium. Tuning laser frequency during the pulse developing is observed as a result. The measurements of the pressure, temperature, and refractive index changes in an RF pulsed excited CO2 slab-waveguide laser are purposes of the work. The pressure changes are measured with calibrated microphones situated close to the laser plasma. The temperature changes are calculated via measured refractive index characteristics, and simple formulas linking the refractive index with the gas density. The picture of the acoustic wave propagation in the laser cavity is presented. The obtained results give the picture of the laser plasma behavior during the pulsed excitation. It leads to a single frequency pulsed laser operation design.
In this paper we present our first experiments and results connected with a laser fiber interferometry. Basic set-up of a fiber vibrometer based on interference weak scattered light with a reference beam shows in this case that signals from photodetector are quite small and often it is impossible to detect them correctly. When the fiber interferometer works on the telecommunication wavelength 1550nm, it is a possibility to use the telecommunication fiber amplifier to gain weak optical signals into levels that are easily detectable.
In this paper we present a new approach to the laser vibrormetry. It is based on the fiber vibrormetry in the third telecommunication window. The scattered light from the vibrating object is guided by a fiber collimator and gained by erbium doped fiber amplifier (EDFA).
The paper describes investigations of vibrations by the laser interferometry where both beams are offset in frequency. This method is called the laser heterodyne vibrometry. The main aim of this investigation was heterodyne detection of a weak laser light scattered from a vibrating object. As a standard surface we used a piece of white zero sheet connected to the vibrating object.