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Schematic of an envisioned SDM-WDM transceiver system that supports N wavelengths × M spatial paths in a fiber link. The arrows indicate the optical signal flows. For example, the transmission capacity can reach 1.2 Pb/s using 120 wavelength (covering C and L bands) times 10 spacial modes at 1 Tb/s per channel (e.g., 100 Gbaud DP-64QAM with a 20% forward error correction (FEC) overhead). A multiwavelength laser system is used for both the input (at the transmitter side) and the local oscillators (at the receiver side). It can be either a high power optical frequency comb or an array of multiplexed single-mode lasers. Its power (including all the wavelengths) is split, equally in the ideal case, into M spatial paths. Each transceiver array consists of N × IQ modulators (IQ-Mod) and coherent receivers (Co-RXs). Pol-Mode (De)MUX, polarization-mode (de)multiplexer.
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The tremendous growth of data traffic has spurred a rapid evolution of optical communications for a higher data transmission capacity. Next-generation fiberoptic communication systems will require dramatically increased complexity that cannot be obtained using discrete components. In this context, silicon photonics is quickly maturing. Capable of m...
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Citations
... Optical communication systems face a continuous data traffic growth to support advanced multimedia and internet of things (IoT) applications [1] and [2]. Several studies have been suggested to increase the transmission capacity of wavelength-division multiplexing (WDM) [3] system by decreasing the channel spacing and increasing the number of channels; up to 281 channels have been reported in C band of 4.5 THz bandwidth [4]. ...
This paper discusses the development of a seven-band coherent wavelength-division multiplexing (WDM) system covering the T to U systems, aiming to enhance the capacity and system efficiency. Seven multiband systems (C+L, S+C+L, S+C+L+U, E+S+C+L, E+S+C+L+U, O+E+S+C+L+U, and T+O+E+S+C+L+U) are designed with 40 GBaud symbol rate, 50 GHz channel spacing, and dual-polarization (DP)-16QAM signaling. The analysis adopted the enhanced Gaussian noise model, considering the amplified spontaneous emission of inline optical amplifiers and nonlinear interference (NLI) from fiber nonlinear optics, including Kerr effect and stimulated Raman scattering (SRS) which it implemented using Matlab (Ver. 2020b) program. The results show that the optimal powers are -4, -5, -5, -4.5, -3.5, -6, and -4.5 dBm for the seven WDM systems, respectively. Further, with a fiber span length of 100 km, the C+L system has the longest transmission reach of 20 span. However, using S+C+L+U system gives the highest bit rate-distance product of 1619 Tbps.km. The O+E+S+C+L+U and T+O+E+S+C+L+U systems are designed with 50 km-span length to reduce the effect of NLI caused by the large numbers of channels (1060 and 1200, respectively).
... Despite several successes, there is a widespread reluctance among the epitaxial growth community to address the challenges in making devices for renewable energy, optical imaging, sensing, and detection needs. To improve SL-based devices with expanded functionalities and reduction in sizes, the use of III-Ns [89][90][91][92][93] and C-based IV-IV materials has recently [94][95][96][97][98][99][100][101][102][103] progressed in creating mid-infrared (MIR) devices for high-temperature electronics, healthcare, photovoltaic, and automotive industry requirements. ...
... With excellent optical properties of Si, many integrated passive and active devices are instigated due to the high refractive index contrast waveguides of Si on insulator (SOI). The exploration of novel materials with ultra-low loss and high electro-optic coefficients are examined to realize advanced PICs with monolithically integrated light sources and efficient modulators [94][95][96][97][98][99][100][101][102]. In this context, Si1−xGex alloys are well established in the photonic and electronic industries [114]. ...
Carbon-based novel low-dimensional XC/YC (with X, Y ≡ Si, Ge, and Sn) heterostructures have recently gained considerable scientific and technological interest in the design of electronic devices for energy transport use in extreme environments. Despite many efforts made to understand the structural, electronic, and vibrational properties of XC and XxY1−xC alloys, no measurements exist for identifying the phonon characteristics of superlattices (SLs) by employing either an infrared and/or Raman scattering spectroscopy. In this work, we report the results of a systematic study to investigate the lattice dynamics of the ideal / as well as graded SLs by meticulously including the interfacial layer thickness (≡1–3 monolayers). While the folded acoustic phonons (FAPs) are calculated using a Rytov model, the confined optical modes (COMs) and FAPs are described by adopting a modified linear-chain model. Although the simulations of low-energy dispersions for the FAPs indicated no significant changes by increasing , the results revealed, however, considerable “downward” shifts of high frequency COMs and “upward” shifts for the low energy optical modes. In the framework of a bond polarizability model, the calculated results of Raman scattering spectra for graded SLs are presented as a function of Special attention is paid to those modes in the middle of the frequency region, which offer strong contributions for enhancing the Raman intensity profiles. These simulated changes are linked to the localization of atomic displacements constrained either by the XC/YC or YC/XC unabrupt interfaces. We strongly feel that this study will encourage spectroscopists to perform Raman scattering measurements to check our theoretical conjectures.
... Silicon photonics-based components offer on-chip functionalities, including polarization diversity circuits, wavelength and space division multiplexers, and a variety of passive and active components. These components enable efficient scaling of optical networks in terms of size, energy consumption, and cost [127]. In the presented thesis study, the first three physical dimensions, namely frequency, quadrature, and time, are implemented using silicon photonics to enhance the transmission capacity of the optical network. ...
The escalating communications traffic in optical networks has driven the exploration of signal manipulation in the optical domain as a promising technology in the last two decades. The surge in data traffic results from the rapid expansion of distributed computing, sensor networks, artificial intelligence, machine learning, and cloud-based services. As we enter the era of quantum communication, autonomous driving, and 6G, the global data flow continues to grow exponentially. Traditional electronic systems have been instrumental in improving signal transmission and reception quality through electronic signal processing. However, they suffer from limitations such as finite operational bandwidth, signal degradation over transmission lines, latency issues, susceptibility to electromagnetic interference (EMI), high power consumption, and cost constraints.
Optical signal processing enabled by silicon photonics offers a solution with significantly higher bandwidth capabilities and faster data processing, along with cost-effective and lowlatency systems. Photonic devices are immune to environmental radiation and EMI, making them suitable for space and quantum applications. Silicon photonic technology has further propelled the application field harnessed by photonic integrated circuits, with matured CMOS-compatible fabrication enabling the development of high-performance optical processing units. The convergence of electronics and photonics on silicon photonic platforms has resulted in significant advancements in the field of optical communications and microwave photonics. This thesis explores the advancements in the field of silicon photonics aggregated with innovative optical signal processing to achieve pivotal improvements in novel methods for signal generation and measurement. It evaluates the performance of various silicon modulators in terms of data transmission and sinc-pulse sequence generation. These silicon modulators are utilized to develop novel photonic-assisted architectures to enhance the transmission channel capacity of the Nyquist transceiver system by addressing the limitations of the analog output bandwidth of generators and receivers in conventional optical transceiver systems. Furthermore, the presented research delves into silicon photonics for microwave photonics applications with the implementation of passive and active photonic devices. The study presents integrated photonic frequency measurement systems, showcasing their superior performance in real-time temporal and spectral analysis of micro and mm-wave signals with best-in-class measurement resolution and accuracy.
... The remarkable multiple degrees of freedom (DOFs) possessed by light, including large bandwidth and high-speed transmission capabilities, make photonic technology an extremely promising platform for high-speed communication and high-performance computing in information science. [1][2][3] Over the last decade, metasurfaces have emerged as an unprecedented approach for manipulating light in various DOFs using compact, artificial two-dimensional nanostructures. 4,5 Metasurfaces have demonstrated significant promise for a wide range of applications in both fundamental science and industry, including wavefront shaping, 6,7 polarization control, [8][9][10] imaging, 11,12 spectrometry, 13,14 and computation. ...
... 15 Recently, considerable research efforts have been devoted to developing metasurfaces to achieve tunable or reconfigurable functionalities. 3,16 A high-speed spatiotemporally controlled metasurface possesses the potential to facilitate novel physics and practical applications within the realm of photonic technology. Numerous materials and strategies have been proposed to empower tunable metasurfaces, including the utilization of phase-change materials, liquid crystal, thermo-optic effect, and electro-optic effect. ...
... The so-called phase mask method, a repeated exposure, or numerous post processing techniques can be also utilized for the formation of a phase-shifting region inside of the grating. An experimentally demonstrated 19.5 ns group delay was observed in a 2 cm long FBG with an index modulation of 1.69 × 10 −3 in the SMF-28 optical fiber, highlighting the benefits of accurate apodization [18][19][20]. ...
This paper describes design, theoretical analysis, and experimental evaluation of a π-Phase-Shifted Fiber Bragg Grating (π-PSFBG) inscribed in the standard telecom fiber for slow light generation. At first, the grating was designed for its use in the reflection mode with a central wavelength of 1552 nm and a pass band width of less than 100 pm. The impact of fabrication imperfections was experimentally investigated and compared to model predictions. The optical spectra obtained experimentally show that the spectral region used for slow light generation is narrower (less than 10 pm), thus allowing for too-low levels of slow light optical-output power. In the next step, the optimization of the grating design was conducted to account for fabrication errors, to improve the grating’s spectral behavior and its temporal performance, and to widen the spectral interval for slow light generation in the grating’s transmission mode. The targeted central wavelength was 1553 nm. The π-PSFBG was then commercially fabricated, and the achieved parameters were experimentally investigated. For the region of (1551–1554) nm, a 15-fold increase in the grating’s pass band width was achieved. We have shown that a pair of retarded optical pulses were generated. The measured group delay was found to be ~10.5 ps (compared to 19 ps predicted by the model). The π-PSFBG operating in its transmission mode has the potential to operate as tunable delay line for applications in RF photonics, ultra-fast signal processing, and optical communications, where tunable high precision delay lines are highly desirable. The π-PSFBG can be designed and used for the generation of variable group delays from tens to hundreds of ps, depending on application needs.
... Advanced modulation systems with coherent detection have been developed to improve spectral efficiency [6,7]. In addition, wavelength, space, and polarization multiplexing have been explored as means to increase transmission capacity, with polarization multiplexing having the potential to double it [8][9][10][11]. The integration of dual-polarization circuits is not only desirable for optical communications but it also plays a critical role in applications such as sensors and signal processors [12,13]. ...
Integrated silicon nitride polarizers play a critical role in the design of complex integrated devices such as filters, switches, and large Mach-Zehnder interferometer networks. These devices require precise control of both polarizations on a single circuit. In addition, polarizers are essential to accurately characterize these devices, primarily due to the low efficiency and polarization extinction ratio (PER) of the surface coupling gratings used in CMOS-compatible silicon nitride platforms for test-specific optical I/O. In this article, we present the design and experimental performance of six prototypes of TE-reflector/TM-pass polarizers specifically optimized for the C-band. These prototypes resemble subwavelength gratings with several additional intricate aspects. In particular, the longer prototypes feature two distinct regions, one representing non-intuitive tapers and the other showcasing a more distinct subwavelength grating. We achieve a high TM transmission efficiency of −0.28 dB along with a PER of 18.2 dB. These results are obtained with a device occupying an area as low as 11 µm × 2 µm, setting a new performance benchmark for compact polarizers compatible with standard silicon nitride platforms.
... In recent years, QD lasers have been repeatedly reported as competent light sources for silicon-based photonic integrated circuits (PICs) [16][17][18][19][20], that are designed not only for optical transceivers but also for other advanced applications where low noise from the laser source is imperative such as in chip-scale gyroscope and quantum cryptography, to name a few. In the telecom field, as the data traffic ramping-up is kept accelerating, scaling up transmission capacity is still necessary, therefore the utilization of low-cost kHz and sub-kHz local oscillators are required to leverage accessible 800 GBaud data rate [10,21]. For an integrated gyroscope, in order to make the most accurate rotational measurement devices, the light source needs to achieve low noise to improve the measurement accuracy for different scenarios [22]. ...
This paper demonstrates that the linewidth enhancement factor of quantum dot lasers is influenced by the external carrier transport issued from different external current sources. A model combining the rate equation and semi-classical carrier noise is used to investigate the different mechanisms leading to the above phenomenon in the context of a quantum dot distributed feedback laser. Meanwhile, the linewidth enhancement factor extracted from the optical phase modulation method shows dramatic differences when the quantum dot laser is driven by different noise-level pumps. Furthermore, the influence of external carrier noise on the frequency noise in the vicinity of the laser’s threshold current directly affects the magnitude of the linewidth enhancement factor. Simulations also investigate how the external carrier transport impacts the frequency noise and the spectral linewidth of the QD laser. Overall, we believe that these results are of paramount importance for the development of on-chip integrated ultra-low noise oscillators producing light at or below the shot-noise level.
... Doerr et al. fabricated a silicon photonic integrated transmitter and receiver that can operate in the wavelength range from 1260 to 1630 nm, covering all the bands from the O to L band [16]. Silicon photonics are also integrated as modulators to provide ultrawideband modulation [16] due to the broadband nature of the plasma dispersion effect [17]. Sena et al. fabricated a dual-polarization IQ modulator based on indium phosphide with proper multi-mode interference designs for low variation of splitting ratio and high spectrum availability [18]. ...
Multi-band transmission over existing fibers would be a key strategy for ongoing capacity expansion even though upgrading from the conventional C band to multi-band, such as the ${\rm C} + {\rm L}$ C + L -band transmission being deployed by operators, would be a slow and complex process. After the ${\rm C} + {\rm L}$ C + L band, which band should be upgraded first in the next stage is an open question. We try to answer this by proposing three different band upgrade strategies, including near-to-far, far-to-near, and performance-prediction strategies, and comparing the potential capacity increase and the investment cost to upgrade different bands. We introduce an optical signal-to-noise ratio (OSNR) estimation model comprehensively covering various impairments to evaluate the quality of transmission of an optical channel and develop what we believe to be a novel method to find optimal launch powers for optical channels. Along with routing and spectrum assignment, an OSNR-aware traffic grooming algorithm is also developed to evaluate the capacity that can be achieved after upgrading different bands in an optical network. Our study shows that the performance-prediction strategy always outperforms the other two strategies. When capacity is considered a key performance metric, the E band should be the first to be upgraded next since it both expands the transmission capacity significantly using only a few additional amplifiers and the band upgrade sequence should be E, O, S, and U. For the performance-prediction strategy, we also evaluate the impact of the upgraded band on the performance of other bands. It is found that the upgraded band always has a significant impact on adjacent bands, with the upgrade of high-frequency bands improving the performance of existing low-frequency bands and the upgrade of low-frequency bands degrading the performance of existing high-frequency bands. In addition, the “ ${\rm C} + {\rm L} + {\rm E} + {\rm O} + {\rm S} + {\rm U}$ C + L + E + O + S + U ” scenario can achieve 3 times the capacity of the “ ${\rm C} + {\rm L}$ C + L ” scenario when all the bands are upgraded.
... Grating structures are widely used in optical interconnection and signal processing [85]. Gratings can be regarded as 1D photonic crystals, which can be used in high-speed MZ modulator for slow light enhancement [86]. ...
This paper reviews the progress of electro-optic modulators composed of silicon-based microscopic photonic structures. The basic principles, device structures, and advanced modulation capability of different geometric types are detailed for micro-ring modulators, photonic crystal modulators, and other related modulators. We illustrate the device operation mechanism with a focus on its photonic aspect and discuss their impacts on the modulator speed, power consumption, and thermal stabilities. The cavity enhancement and slow light effect significantly reduce the device footprint and power consumption, with the trade-off of limited operation wavelength range. Other emerging microscopic photonic structure-based silicon modulators for advanced modulation formats exhibit promising performance for further optimizations. Finally, we discuss the existing challenges and further directions of microscopic photonic structure-based silicon modulators for pertinent applications.
... T HE ever-growing demand for bandwidth drives the development of optical transceivers with higher transmission data rates. Silicon photonics will play an essential role in scaling the transmission capacity of next-generation optical communications systems due to its advantages of cost, footprint, and power consumption, and CMOS compatibility [1], [2]. Recent advances in different modulator structures such as traveling-wave Mach-Zehnder modulators (TW-MZMs), microring modulators (MRMs), and electro-absorption modulators (EAMs) on the silicon-on-insulator (SOI) platform have led to demonstrations at very high bandwidths and date rates [3], [4], [5]. ...
We demonstrate an all-silicon segmented modulator with traveling-wave electrodes, achieving an electro-optic bandwidth beyond 67 GHz and a
$V_\pi$
of 5V. We show that dividing a long optical modulator into shorter segments can help achieve a higher bandwidth without compromising modulation efficiency or optical loss. We analyze the bandwidth limitation due to the delay mismatch between the driving and optical signals. We show that the impact of misalignment of driving delays between segments on the overall bandwidth of the modulator can be described by a finite impulse response filter. Using this modulator, we achieve optical transmission of 120 Gbaud 8-level amplitude shift keying with coherent detection. Taking into account the forward error correction overhead, this yields 336.4 Gb/s net on a single polarization. Our design has the potential for achieving 1 Tb/s using dual-polarization IQ modulation.
