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Test, assembly and packaging processes substantially contribute to the overall production cost of photonic integrated circuits. Implementation of test processes across the full production chain is critical in order to deliver statistically significant data sets. These will allow for optimization of the fabrication process widows, early known-good-die selection, improved models in design tools and lead to improved yield, reduced cost and scalability which will open a path to volume production. Progress on developments of open access test infrastructure at our laboratories and open standard test framework will be presented.

RF frequency downconverters are of key importance in communication satellites. Classically, this is implemented using an electronic mixer. In this paper we explore the use of photonic technology to realize the same functionality. The potential advantages of such an approach compared to the classical microwave solutions are that it is lighter weight, has lower power consumption and can be made smaller if photonic technology is used. An additional advantage is the fact that the optical local oscillator (LO) reference can easily be transported over longer distances than the equivalent LO signal in the microwave domain due to the large bandwidth and low loss and dispersion of optical fiber. Another big advantage is that one can envision the use of short pulse trains as the LO - starting off from a sinusoidal RF reference - in order to exploit subsampling. Subsampling avoids the need for high frequency LO references, which is especially valuable if a downconversion over several 10s of GHz is required. In this paper we present the operation principle of such a photonic frequency downconverter and describe the performance of the developed micro-photonic building blocks required for this functionality. These micro-photonic building blocks are implemented on a III-V semiconductor-on-silicon photonic platform. The components include a micro-photonic hybridly modelocked laser, a 30GHz electroabsorption modulator and an intermediate frequency (1.5GHz) photodetector.

Optical sensing offers unrivalled precision with real-time monitoring, but the complexity in implementing the optical sources has so far limited deployments to high value measurement systems. Innovations in photonic integration are beginning to enable breakthroughs in terms of cost, size and performance. Integrated sources and readouts can be created with large-scale semiconductor wafer production techniques. InP integrated photonics is able to combine best-in-class components including the lasers and amplifiers within one photonic chip. The chip-scale integration of complete circuits enables on-chip stabilisation and environmental corrections for further advances in measurement precision and at lower power consumption.

A novel operation mode field reconfigurable DBR laser is designed, realized and investigated experimentally. With different controlling of the same hardware, a shared-cavity six-section DBR laser diode can be flexibly configured to operate as a continuous wave or a pulsed wave laser.

We present our recent work on the realization of III-V-on-silicon mode-locked lasers and integrated nonlinear waveguides for the realization of integrated frequency combs.

Monolithic integration of four widely tunable extended cavity lasers suitable for gas detection is presented. Each laser features a precise, grid-less tuning mechanism with a low-linewidth, single-mode output over a wide wavelength range of 74nm.

The authors demonstrate the generation of a highly coherent multicarrier signal that consists of eight clearly resolved 10.7-GHz coherent sidebands generated within 3 dB of the spectral envelope peak and with an extinction ratio in excess of 45 dB by gain switching a discrete mode (DM) laser. The generated spectral comb displays a corresponding picosecond pulse train at a repetition rate of 10.7 GHz with a pulse duration of 24 ps and a temporal jitter of ~450 fs. The optical spectra and associated pulses of the gain-switched DM laser are subsequently compared with a gain-switched distributed feedback (DFB) laser that generates a spectrum with no discernible sidebands and corresponding pulses with ~3 ps of temporal jitter. By means of external injection, the temporal jitter of the gain-switched DFB laser is then reduced to

This paper presents experimental investigations of the all-optical synchronization of a distributed Bragg reflector (DBR) laser self-pulsating at 40 GHz on various injected bit-rate signals. Even though there is no modulation applied to this laser, it exhibits a modulation of its output emission, measured at 39.7 GHz with a linewidth of 30 MHz. Such performance is exploited in all-optical clock recovery for a return-to-zero data stream at 40 Gbit/s. The SP-DBR laser wavelength and the injected signal wavelength are 10 nm apart. All-optical synchronization is demonstrated at 40 Gbit/s with a linewidth of less than 20 MHz for injected signals at 10 and 20 Gbit/s, respectively. Thus the SP-DBR laser proves to be very versatile and can be synchronized on various bit-rate data signals.

Wavelength tunability of an all-optical clock recovery operation based on a quantum-dash mode-locked Fabry-Perot laser diode is experimentally investigated. Synchronization of the device to the injection of 40-Gb/s nonreturn-to-zero (NRZ) incoming data is assessed by analyzing both the carrier-to-noise ratio and the linewidth of the 40-GHz beat-tones measured at the mode-locked laser output. Under optical injection, beat-tone linewidths below 10 Hz are measured. Recovered clock pulses featuring a width of 1.6 ps are obtained irrespective of the wavelength detuning between the laser spectra and the optical carrier of the incoming data stream.

We propose a simple potentially integrable configuration for expanding a wavelength tunable comb by cascading gain switched Fabry-Pe´rot lasers. A 10GHz spaced comb, exhibiting 13 coherent low-linewidth tones within a 3 dB window, and tunable over 20 nm is demonstrated.

A passively mode locked extended cavity quantum well ring laser at 1.58 µm with repetition rate of 2.5 GHz in the form of a photonic integrated circuit is presented. The device is realized using InP based active-passive integration technology. The 33mm long cavity contains gain, saturable absorption and passive waveguide sections as well as a phase shifter sections to enable fine tuning of the spectral position of the lasing modes. Passive mode-locked operation and with wavelength tuning of the laser modes are experimentally demonstrated. This laser is the lowest reported repetition rate for a monolithically integrated ring laser.

A ring mode-locked laser fabricated as a monolithic photonic integrated circuit using a InP based integration technology is presented. It generates an optical coherent comb around 1542 nm with a record 11.5 nm 3 dB bandwidth.

Modal gain characterization of mid-infrared semiconductor optical amplifiers intended for an active-passive integration platform is presented. Measured gain profiles reveal the peak values at around 2.07μm and 3dB bandwidth up to 27nm.

In this paper, we present the experimental investigation of the switching-on and passive mode-locking times of a Fabry-Perot quantum dash laser diode. Their values are 30ns and 8ns respectively. These times are measured in order to study the phenomenon of mode-locking in this device and its potential application for packet switching networks.

A wavelength tunable optical comb is generated based on the gain-switching of an externally seeded Fabry-Pérot laser diode. The comb consists of about eight clearly resolved 10 GHz coherent sidebands within 3 dB spectral envelope peak and is tunable over the entire C-band (1530 to 1570 nm). The optical linewidth of the individual comb tones is measured to be lower than 100 kHz, and the RIN of the individually filtered comb tones (-120 dB/Hz) is shown to be comparable to the entire unfiltered comb (-135 dB/Hz). Besides, expansion of the tunable gain switched comb is achieved with the aid of an optical phase modulator, resulting in near doubling of the number of comb tones.

A novel and cost effective long reach PON downlink scenario is proposed employing a multi-carrier transmitter and pilot tone aided direct detection at the receiver. Error free performance with QPSK and 50km transmission is presented.

Linewidth narrowing of the radio frequency beat-tones and the optical-modes is experimentally investigated in a ∼40 GHz quantum-dash mode-locked laser diode subject to optical injection of 10 GHz pulses. In comparison to the 75 kHz linewidth exhibited by the beat-tones in passive mode-locking conditions, a remarkable reduction to less than 8 Hz is achieved when the laser is under optical injection. From this beat-tone signal, an integrated root-mean-square timing jitter of 64 fs is calculated. In addition, a quadratic profile of the optical linewidth with the wavelength is observed in active locking, reaching a minimum of 1.7 MHz for the longitudinal modes around 1530 nm and progressively increasing to 37.4 MHz for modes at 1525 nm.

Optical frequency comb sources (OFCS) have recently attracted a lot of interest due to wide ranging applications such as optical arbitrary waveform generation [1], photonic microwave signal generation [2], optical signal processing [3] and multi-carrier spectrally efficient transmission techniques with the sub-channel spacing equal to the symbol rate of each sub-channel [4]. OFCS with good spectral flatness, stability and low linewidth are highly desirable for such applications. One of the conventional approaches used in realizing a comb source is based on mode-locked semiconductor and fibre lasers [5]. Although this technique can generate multi-carrier signals spanning over a wide bandwidth, it inherently suffers from cavity complexity and does not offer the free spectral range (FSR) tunability since the comb line spacing is fixed by the cavity length of the laser. Moreover, the optical linewidth of the individual comb lines can be relatively large (several MHz) preventing higher order (or low baud rate) advanced modulation formats to be imposed. Another technique that has been reported entails the use of a single, cascaded or dual drive Mach-Zehnder modulators (MZM) to generate the phase correlated optical frequency comb [6]. Although this technique provides a relatively flat optical comb, the large insertion loss of the modulator coupled with the modulation efficiency can prove prohibitive. The extra optical component also adds to the cost and complexity of the transmitter, rendering this technique unsuitable for short reach applications.

Synchronization of a 40 GHz quantum-dash mode-locked Fabry-Perot laser diode with optically injected pulse streams is experimentally studied by analyzing the linewidth of the associated 40 GHz beat-tones. Injected signals consist of trains of 1.6 ps pulses at various repetition rates, spanning from 10 to 160 Gb/s of encoded or not with pseudo-random on-off key data sequence. Data injections at the fundamental bit-rate (40 Gb/s), harmonic at 80 and 160 Gb/s and sub-harmonic at 10 and 20 Gb/s are used to synchronize the mode-locked laser. The response is a stable 40 GHz clock pulse train featuring a width of 1.8 ps. Moreover, the 40 GHz beat-tones associated to the recovered clock pulses exhibit a full-width at half maximum smaller than 8 Hz regardless of the injected data rate. It is observed that frequency components at 10 and 20 GHz do not create any amplitude modulation on the recovered 40 GHz clock pulses by the injection of data signals at 10 and 20 Gb/s. Similarly, synchronization of the quantum-dash laser with pulse streams at 80 and 160 Gb/s is sustained in spite of negligible components at and below 40 GHz are injected in these two data rates.

There is a vast interest in multi-wavelength light sources which can find applications in optical communications [1], and photonic generation of millimetre and terahertz signals [2]. For such applications highly coherent and stable optical comb sources, with uniform power distribution among frequency components are desirable. Conventional comb sources are mainly based on mode-locked semiconductor and fibre lasers. Both are penalized by fixed free spectral range (FSR), and complexity of the epitaxial growth in the first case, and stability issues due to long cavity lengths in the latter. Another technique, which offers the advantage of tuneable FSR, entails the use of electro-optic modulators. This however, requires the use of expensive dual drive modulators [3], or a series of cascaded modulators [4], in order to achieve a broad and relatively flat comb.

Performance improvement of a directly modulated 10 Gb/s OFDM system by optical injection of monolithically integrated lasers is shown experimentally over differing fibre lengths. The modulation and optical injection is performed using monolithically integrated Discrete Mode lasers. It is shown that optical injection with this device reduces third order inter-modulation distortion by up to 10dB and this results in an improvement in system performance from above a forward error correction BER threshold of 1 × 10(-3) to significantly below it.

Experimental measurements on a quantum dash mode-locked Fabry-Perot laser are presented. Its potential for clock recovery at 40 Gb/s in an all-optical 3R regeneration with an NRZ-to-RZ format conversion and wavelength offset of 23 nm is demonstrated.

A narrowband terahertz signal generated by a uni-travelling carrier photodiode (UTC-PD) interfaced with a dual-mode Fabry-Perot laser diode is demonstrated. A beat tone corresponding to the free spectral range is generated on the UTC-PD, and radiated by a transverse-electromagnetic-horn antenna. All components involved in this experiment operate at room temperature. The terahertz signal at a frequency of 372 GHz is recorded, and the linewidth is 17 MHz. The linewidth and the tunability of the emitted terahertz wave are analyzed, as a function of the laser bias.

An experimental analysis of the timing jitter associated with sub-picosecond pulses produced from a quantum dash passively mode-locked Fabry-Perot laser is produced. Moreover, application as an all-optical clock recovery function for a 40Gb/s data rates with non-return-to-zero (NRZ) modulation format is demonstrated using this laser.

A bulk semiconductor optical amplifier (SOA) utilizing a multi-contact biasing method is characterized as a function of the bias current supplied to each section Firstly, amplified spontaneous emission spectra and characteristic light-current profiles are analyzed. Single-pass gain and noise figure of the SOA are then assessed by injecting a continuous wave input beam. Finally, the amplification of a 10 Gb/s (215-1) long pseudo random bit sequence signal is analysed. The obtained results, particularly at a bias condition of 90mA-50mA-10mA, reveal the potential of this device as a low noise figure in-line amplifier.

Wave-mixing at 370-GHz in a SOA and FP semiconductor laser is investigated by using a FROG-system. A comparison of the optical time-fluctuations measured at their output stresses the importance of a resonant cavity in THz-signals generation from semiconductor optical devices.

Generation of sub-picosecond pulses by a dc-biased passively mode-locked Fabry-Perot laser is demonstrated. By using a tunable band-pass filter, it is observed that the width of the generated pulses decreases in direct proportion to the optical modes emitted by the laser. Furthermore, performing a passive compression by a piece of single mode fiber, we demonstrate the generation of 720 fs pulses by this type of mode-locked Fabry-Perot laser.

Generation of narrow microwave signals produced from the mode beating of a DBR laser is presented. The application of this process to the cw-THz wave generation is also demonstrated using a slotted FP laser.

In this paper, Cassidy's method is presented and is applied to measure the linewidth enhancement factor (LEF) of a 370 GHz self-pulsating Fabry-Perot laser. The importance of the LEF is addressed, the method is detailed, and the device under test is presented. It exhibits a self-modulation at 370 GHz even though it is DC biased. The measured LEFs vary according to the wavelength, values of 4 have been measured at threshold current, which is typical in the case of multi-quantum well lasers. In this paper we propose to present measurement of the linewidth enhancement factor (LEF) in semiconductor laser based, 370 GHz source generator. First we explain the origin of LEF in semiconductor material, then we present several techniques to measure it. We present a computational simulation using modelled ASE spectra, and in part 4, we detail our device and experimental set-up and provide some results. The linewidth enhancement factor (LEF) or alpha parameter is a distinguishing feature of semiconductor devices. Semiconductor devices generally have a larger linewidth than other solid state lasers. This broadened linewidth leads to effects such as mode instability, filementation in broad area devices and frequency chirping under modulation. This last effect is of particular interest, especially in the field of optical communications. It can be suppressed if the LEF is reduced. Therefore in the design of semiconductor lasers or semiconductor amplifiers (SOA), a number of factors have to be taken into consideration, but one of the most important of these is the linewidth enhancement factor. For instance, when the gain of an SOA is affected by the injection of a pulsed source, refractive index changes caused by changes in carrier density will lead to an instantaneous variation of the frequency. This effect is exacerbated as the gain is saturated.

Characterizations of passively mode-locked semiconductor lasers will be presented in following paper. These lasers are able to operate in multimode regime and to exhibit a modulation of output power even though they are DC-biased. A frequency of the modulation corresponds to their free-spectral range associated with optical longitudinal modes. Some potential applications for devices of that type will be disclosed: in THz frequency range for terahertz wave generation at room temperature without any direct modulations applied, in the radio frequency range ability to synchronise their modulation to the bit-rate of an incoming signal makes them suitable for all-optical clock extraction.

Multimode semiconductor lasers under certain DC bias conditions generate electromagnetic waves from the beating between the longitudinal lasing modes. The frequency of those waves is directly related to the free spectral range of the involved modes. Our recent experimental work is carried out on slotted Fabry-Perot lasers with mode separation of 330 GHz. The devices are at room temperature biased at 3 times the threshold current. Using a bolometer coupled to an FT-IR interferometer we are able to observe radiation at 660 GHz, in the terahertz range.

Although self pulsating (SP) lasers are DC biased, they feature a modulation of the output power. For the results presented in this paper, the SP frequency corresponds to the frequency spacing between longitudinal modes or its second harmonic. The performances of both a 40 GHz self pulsating distributed Bragg reflector laser and of a 660 GHz slotted laser are presented. For the first laser, the radio frequency (RF) signal was analysed on electrical spectrum analyser and its linewidth was smaller that the sum of the main optical modes, proving a passive modelocking of the mode phases. For the slotted laser, a bolometer interfaced to a FT IR spectrometer is used for the terahertz (THz) detection. A signal 10 times larger than the noise level was measured with this set up. Both lasers have demonstrated to be an easy solution to produce RF or THz signal generator.

A compact and fabrication-tolerant integrated remotely tunable optical delay line is proposed for millimeter-wave beam steering and is fabricated in an InP generic foundry. The proposed delay line is based on a spectrally cyclic-arrayed waveguide grating feedback loop. Its major features include the tolerant architecture with reduced chip size, and bi-directional operation with simplified remote tuning. Moreover, its cyclic feature guarantees further cascaded operations either for 2D radio beam steering or for high-resolution delay generation. The experimental results show less than 6.5-dB insertion loss of the integrated delay line. Five different delays from 0 to 71.6 ps are generated with less than 0.67-ps delay errors.

A mode-locked extended cavity quantum well ring laser at 1.58 μm with a repetition rate of 2.5 GHz in the form of a photonic integrated circuit is presented. The device is realized using InP-based active-passive integration technology. The 33 mm long cavity contains gain, saturable absorption, and passive waveguide sections as well as phase shifter sections to enable fine tuning of the spectral position of the lasing modes. Passive and hybrid mode-locked operation, along with the wavelength tuning of the laser modes, are experimentally demonstrated. In the passive mode-locking regime, a beat signal at the fundamental round trip frequency with a 3 dB bandwidth of 6.1 kHz is produced on a fast photo diode.

An all-optical heterodyne approach based on a room-temperature controlled semiconductor optical amplifier (SOA) for measuring the frequency and linewidth of the terahertz beat-tone signal from a passively mode-locked laser is proposed. Under the injection of two external cavity lasers, the SOA acts as a local oscillator at their detuning frequency and also as an optical frequency mixer whose inputs are the self-modulated spectrum of the device under test and the two laser beams. Frequency and linewidth of the intermediate frequency signal (and therefore, the beat-tone signal) are resolved by using a photodiode and an electrical spectrum analyzer.

Linewidth narrowing of the radio frequency beat-tones and the optical-modes is experimentally investigated in a ∼40 GHz quantum-dash mode-locked laser diode subject to optical injection of 10 GHz pulses. In comparison to the 75 kHz linewidth exhibited by the beat-tones in passive mode-locking conditions, a remarkable reduction to less than 8 Hz is achieved when the laser is under optical injection. From this beat-tone signal, an integrated root-mean-square timing jitter of 64 fs is calculated. In addition, a quadratic profile of the optical linewidth with the wavelength is observed in active locking, reaching a minimum of 1:7 MHz for the longitudinal modes around 1530 nm and progressively increasing to 37:4 MHz for modes at 1525 nm.

We report first demonstration of quantum dash mode-locked laser based open-loop optical clock recovery of 160 Gb/s RZ-OOK after 52 km transmission with 102 fs timing jitter 40 GHz clock and 2 dB BER penalty.