This work presents photonic integrated multi-channel transmitters for free-space optical communication systems applications. The circuits were designed and fabricated using the generic indium phosphide technology, which offers integration of passive and active elements and light amplification within the classical telecom C and L bands. The transmitters comprise an array of DBR laser light sources connected to electro-absorption modulators and an arrayed waveguide grating used as a wavelength multiplexer. The validity of the applied solution was investigated and confirmed with high-speed transmission experiments, including BER and eye diagram measurements of one and two-channel operations. The performance of the transmitters has been verified in the back-to-back configuration, and the first tests of free-space optical transmission have also been performed. The obtained results confirm the applicability of integrated transmitters in novel FSOC systems.
This work presents the designs and performance of a series of photonic integrated interrogators developed and investigated for the last few years by the Eastern Europe Design Hub team at Warsaw University of Technology. The interrogators were designed to monitor dynamic signals from fiber Bragg gratings (FBGs) and manufactured in the generic indium phosphide (InP) platform. In particular, the main design assumptions will be presented, along with parameters initially proven by versatile electrical and optical characterization. Possible applications and further development of solutions for integrated photonic interrogators will also be discussed.
We present and discuss an experimental fiber-optic sensing system developed for application in a coal mine. One of the major issues of coal mine engineering is the condition of the rock mass above the roadways in which miners extract coal. The condition is typically monitored using measurement anchors with electronic strain gauges. In the demonstrated system, the electronic sensors are replaced with FBGs. A fundamental cell of the network consists of gratings that are glued to a special groove on the anchor, while the output signal is read out with an interrogation system. The interrogator is realized either using a commercially available device or with a photonic integrated circuit. The system has been assembled and tested both in the anchor laboratory and in a test site in a roadway of a mine. The first characterization results are promising and prove the feasibility of fiber-optic sensors for rock mass monitoring.
This work presents and discusses the results of developing the first integrated photonic platform for the mid-IR spectral range, MIRPIC (Mid-IR Photonic Integrated Circuits). The platform is based on the heterogeneous integration of mid-IR light sources (QCLs), Ge-on-Si waveguiding components, and mid-IR photon detectors. We will present the platform's general concept along with the library of individual components developed and tested so far, discussing them in the context of operational parameters. Recent results will be showcased, documenting progress in MIRPIC platform development while pointing out the main challenges faced by the technology.
This work has received support from the National Centre for Research and Development through project MIRPIC (TECHMATSTRATEG-III/0026/2019-00).
To increase the data capacity of the telecom systems, new technologies are needed, e.g., mode division multiplexing (MDM), based on the concept of utilizing different mode channels for transmitting the different information streams in the few mode fibers (FMFs). A typical MDM link is composed of a multi-channel transmitter, which generates signals for each spatial mode, a dedicated multiplexer which is used to excite appropriate spatial modes and to launch all of these into a few-mode fiber. A demultiplexer preceding a multi-channel receiver complements the picture of the basic MDM system. This work is focused on proposing a new solution for MDM transmitters, fully utilizing the potential of generic technology of InP-based integrated photonics. Photonic integrated circuits (PICs) offer the possibility of developing a new generation of compact, energy-efficient, and low-cost devices, with additional features of high reliability and ease of integrating the multiple transmitters on a single chip. For the integration of both active and passive optoelectronic elements, indium phosphide (InP) is the material of choice due to the direct band-gap and the possibility of light generation/amplification at the telecom wavelengths around 1.55 µm. The proposed design is discussed with respect to potential performance parameters and applicability in MDM systems. ACKNOWLEDGMENT This work has received partial support from the National Centre for Research and Development through project NMKM+ (TECHMATSTRATEG1/348438/16/NCBR/2018) and from the EU Horizon 2020 research and innovation programme under grant agreement No. 687777 (PICs4All).
Recent advances in integration technologies enable constructing novel, highly complex and miniaturized photonic systems for a large variety of applications. A constantly increasing interest can be observed in implementing application specific photonic integrated circuits (ASPICs) in a new generation of optical sensing systems.
The InP platform allows to realize complete interrogators of sensing systems, comprising the light sources and photodetectors. An InP PIC can also be used as a sensing element itself. In this work we discuss the sensing systems addressing two different application fields, which can benefit from the recent developments of InP platforms - optical gyroscopes and interrogators of fiber Bragg gratings.
The principle of work of optical gyroscope is based on the Sagnac effect. Two typical configurations can be identified – interferometric fiber-optic gyroscope (IFOG) and ring laser gyroscope (RLG). An integrated interrogator unit of an IFOG system presented here was realized using a DBR laser, passive couplers and PIN photodiodes. Characterization results have proven the possibility of detection of the Sagnac signal for the length of the fiber loop of 1 km. We also discuss monolithic single-frequency lasers, which were realized in the framework of the development of an integrated optical gyro.
Also, the integrated interrogators of fiber Bragg gratings are presented and discussed. The investigated solutions are based on the interrogation scheme in which a broadband signal is coupled to a network of FBGs, and the reflected signals are analyzed using a spectrometer based on an arrayed waveguide grating. Several realized circuits are discussed with respect to their design, characterization results and potential for application in sensing systems.
Studies were funded by FOTECH-1 project granted by Warsaw University of Technology under the program Excellence Initiative: Research University (ID-UB). This work was partially supported by National Centre for Research and Development (PBS3/B9/41/2015).
The magnetic resonance imaging (MRI) technique is a powerful diagnostic tool which is nowadays commonly used in many fields of medicine. In some cases, especially of the patients of intensive care units, it is highly recommended or even necessary to provide continuous monitoring of basic physiologic parameters, mainly the heart rate and the respiratory rate, during the MRI scan procedure. The presence of a strong magnetic field within the MRI chamber requires application of non-standard devices and solutions. The monitoring system needs to be immune to the strong magnetic field and simultaneously cannot negatively influence on the results of the scan. Therefore, application of optical sensing technologies could be potentially advantageous to fulfil these requirements. In this work we propose a novel optoelectronic measurement system, dedicated to monitoring of the patient during an MRI scan, immune to strong magnetic field and compatible with the MRI apparatus.
Fiber Bragg gratings (FBGs) are used as the sensing elements – the strain induced by the patient’s respiration and cardiac activity cause a change of the Bragg wavelength. These changes can be accurately measured and monitored in the time domain. The respiratory and heart rate can be extracted by further processing of the measured signal by dedicated software. The gratings are organized in a network to maximize the effective sensing area. Each of the FBGs has a different Bragg wavelength so that they can be connected in series.
The information from the sensors is read out using an interrogator based on an application specific photonic integrated circuit (ASPIC), designed and fabricated in an InP-based generic integration technology. The interrogator comprises a 36-channel arrayed waveguide grating wavelength demultiplexer, which outputs are connected to PIN photodiodes. Such a photonic circuit acts as a spectrometer and allows to reconstruct the reflection spectrum of many gratings simultaneously. An external superluminescent LED is used as the light source, however in the target configuration the source could be monolithically integrated with the interrogator. The Bragg gratings, the interrogator and the SLED are connected with each other using an optical circulator.
Initial tests of the monitoring system have been performed using a single fiber Bragg grating as the strain sensor and a commercially available optoelectronic interrogator. The fiber with an inscribed FBG was mounted using an epoxy glue on a PMMA board and deployed under the patient. Two signals can be distinguished out of the measured waves. The first one, with strong and slowly-varying peaks, reflects the respiration of the patient. The second signal, characterized by low-intensity and fast-varying peaks is a result of the cardiac activity. No influence of the magnetic field of the MRI instrument on the sensing system has been observed. The first results have confirmed both the correctness of the approach and the applicability of the system to monitoring the patient’s physical condition during MRI diagnosis.
This work was supported by the National Centre for Research and Development, project OPTO-SPARE, grant agreement PBS3/B9/41/2015.
The objective of this research is to design, develop and test the InP based multichannel transceivers dedicated for application in WDM access systems. The transmitters are making use of DBR lasers and Mach-Zehnder modulators. The satisfying parameters of transceivers were obtained like low threshold current and good side mode suppression ratio.
Together with the development of fiber optic sensor networks the accurate and reliable operation of dedicated readout instruments became a critical issue. After years of optimizing the interrogating devices the use of photonic integrated circuits (PICs) has opened a new era of highly reliable, compact and versatile devices offering additionally advantages of low power consumption and cost-optimized design.
Considering the most commonly deployed fiber Bragg grating (FBG) based sensor systems/networks, typically two PICs-based solutions for interrogators may be used: an arrayed waveguide grating (AWG) spectrometer with a broadband SLED source or a set of tunable laser sources with a photodiode detector. Among commercially available PIC technologies the InP platform has a substantial advantage as it allows fabrication of both passive devices (waveguide circuitry) as well as active devices (photodiodes and light sources) in the same technological process.
In this work we investigate two different layouts of AWG-based integrated interrogators fabricated in generic technology of indium phosphide. We analyze the influence of crosstalk between AWG channels on operation of the device and possibility of interrogating narrow-band FBG reflection peaks as well as the influence of input polarization state on the AWG response, which is of fundamental importance for proper operation of an integrated FBG interrogator. As there is no polarization control elements available at present in the offer of generic InP technology providers we discuss the possibility of using off-chip solutions exploiting additional fiber-optic components. As a possible alternative to AWGbased interrogators, we discuss also the possibility of using integrated tunable lasers for FBG interrogation.
In this work a study on three different concepts of photonic integrated multichannel transmitters for applications in WDM-PON access systems is presented. The devices differ in design of the main components of the chip – the lasers and modulators are optimized for different technology platforms. All are compared and analyzed with respect of the fundamental parameters like spectral and power characteristics of the lasers and performance of the amplitude modulators. The transmitters were designed in a generic approach and fabricated in multi-project wafer runs as InP-based monolithic photonic integrated circuits.
Recently observed dynamic development of photonic integrated circuits (PICs) technology enabled significant broadening of potential application area, initially focused on high speed optical communication. One of the prospective and emerging fields is optical sensing, where photonic chips can play twofold role of an optical interrogator and an optical transducer itself. In this paper we discuss the possibilities and perspectives of deploying PIC-based solutions for both these applications.
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