St Stanislaw Stopinski

An introduction to InP-based generic integration technology

Photonic integrated circuits (PICs) are considered as the way to make photonic systems or subsystems cheap and ubiquitous. PICs still are several orders of magnitude more expensive than their microelectronic counterparts, which has restricted their application to a few niche markets. Recently, a novel approach in photonic integration is emerging which will reduce the R&D and prototyping costs and the throughput time of PICs by more than an order of magnitude. It will bring the application of PICs that integrate complex and advanced photonic functionality on a single chip within reach for a large number of small and larger companies and initiate a breakthrough in the application of Photonic ICs. The paper explains the concept of generic photonic integration technology using the technology developed by the COBRA research institute of TU Eindhoven as an example, and it describes the current status and prospects of generic InP-based integration technology.

Monolithically integrated 8-channel WDM reflective modulator

In this work the design and characterization of a monolithically integrated photonic circuit acting as a reflective modulator for eight WDM channels is presented. The chip was designed and fabricated in a generic integration technology.

Photonic Integrated Multichannel WDM Modulators for Data Read-Out Units

This study presents the recently developed monolithic photonic-integrated circuits that provide efficient amplitude modulation for wavelength division multiplexed optical channels. The circuits were designed for application as a read-out unit in a high-energy physics experiment, and are sufficiently general to be applied in various types of high-speed photonic transmitters. They were constructed using basic building blocks provided in an indium phosphide-based generic integration technology process and fabricated in a multi-project wafer run. Two variants of the circuits, utilizing modulators in Mach-Zehnder and Michelson interferometer configuration, are discussed. A modulation bandwidth of 18.6 GHz was measured and error-free transmission of a 10-Gb/s signal through 85 km of optical fiber was achieved.

Development of InP-based multichannel transmitters for application in WDM access systems

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.

Integrated interrogator circuits for fiber optic sensor network in generic InP photonic integrated circuit technology

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.

Noninvasive optoelectronic system for monitoring of the heart and respiratory rate of the patient exposed to MRI scanning (Conference Presentation)

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.

An interferometrie fiber-optic gyroscope system based on an application specific photonic integrated circuit

Optical sensing techniques are considered as one of the most advancing and extensively investigated fields of photonics technologies. The fundamental advantages of optical sensors such as immunity to electro-magnetic interference, compact size and energy efficiency designate them to use in highly requiring applications, e.g. in harsh environment and aviation. Modern optical gyroscope systems, which are a critical part of inertial measurement units (IMU) of contemporary airplanes, drones, spacecrafts and others, are definitely one of the most impressive examples of successful implementation of photonic sensors [1]. Typically, the angular velocity is measured by utilizing the Sagnac effect occurring in rotating optical medium, which can be either an optical fiber loop or a ring laser [2]. Nowadays, commercially available gyroscopes are realized using discrete optoelectronic components, while in this work we present and discuss an interferometric fiber-optic gyroscope (IFOG) system, which uses a monolithic application specific photonic integrated circuit (ASPIC) as the readout device. The chip has been realized using the generic foundry approach [3]. We expect that application of such a compact photonic circuit will lead to reduction of the sensor weight and energy consumption with simultaneous increase of reliability of the device.

Sensing applications of photonic integrated circuits: ultra-compact optical transducers and interrogators

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.

Monolithically integrated multichannel transmitters for application in WDM-PON systems

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.

A Photonic-Integrated Transceiver for Data Readout Systems

This study presents a photonic integrated transceiver for application in a data readout unit of a sensor network. The device was realized in a generic InP-based technology. The circuit uses an asymmetric coupler and a PIN photodiode for input signal detection and a Mach-Zehnder amplitude modulator for encoding of output sensor data. Small-signal modulation bandwidth of 11.1 GHz was measured, eye-diagrams with a dynamic extinction ratio of 11 dB were recorded, and transmission of a 10-Gb/s signal over 25 km of SMF fiber with bit error rate below 10-10 was achieved.