KEYWORDS: Design and modelling, Modulation, Telecommunications, Optical communications, Optical coherence, Mathematical optimization, Control systems, Oscillators, Digital signal processing, Crosstalk
Carrier leakage in the transmission spectrum can significantly impair the performance of coherent optical communication systems. Though a common occurrence, the underlying causes remain ambiguous and not clearly analyzed. This paper embarks on a systematic exploration of the sources of carrier leakage, proposing resolutions across different dimensions. These insights aim to pave the way for enhancing system performance, thereby contributing to the burgeoning field of coherent optical communications.
The growing demand for global communication services necessitates high bandwidth interconnects. With a gradual maturity in the spectral efficiency (SE) growth, extending optical bandwidth beyond the C + L-band is crucial for future optical network upgrades. Silicon photonics (SiPh) technology has already been practically implemented in short-reach optical interconnects and coherent communication links, due to the advantages in size, cost, and power consumption. Despite its commercial success, achieving a high extinction ratio (ER) with wide optical bandwidth in the volume production poses difficulties. In this paper, a power compensation method is proposed and investigated theoretically and experimentally. Compared to the convention method, our algorithm is still robust in a large range of extinction ratio from 10 dB to 45 dB, when the other child Mach–Zehnder modulator (MZM) is non-ideal and other noise exists. The new ER compensation method will be very useful in wide optical bandwidth transceivers.
We build three different schemes for 800G ICR (integrated coherent receiver) S21 testing. By analyzing the accuracy, repeatability, efficiency, dynamic range etc., we can get their advantages and disadvantages, which will guide our choice for proper 800G ICR testing.
We present an improved 400G chip/device level Integrated Coherent Receiver (ICR) optical-electronic testing system based on the system last year [1]. It shows high repeatability and high accuracy compared with commercial system. This new system can greatly promote the efficiency, and it is also compatible for 100G/400G chip level test and device level test. What’s more, the system can get most of important parameters of ICR automatically.
KEYWORDS: Modulators, Printed circuit board testing, Digital signal processing, Optical character recognition, Transmitters, Telecommunications, Signal to noise ratio, Nyquist pulse, Standards development, Signal attenuation
The influence of the driver frequency peaking on the coherent transmission system is carefully discussed in the study. It is found that the driver peaking can interact with its nonlinearity and the bandwidth of the modulator should be large enough to ensure that the peaking of the driver to be a moderate value.
Although silicon photonics (SiPh) has already been developed as a commercial technology, further improvements are under investigation to increase the yield in the volume production. Extinction ratio (ER) is one of the important characteristics of a SiPh Mach–Zehnder (MZ) in-phase and quadrature (IQ) modulator. Besides the chip design, waferlevel or chip-level testing becomes efficient for the ER yield improvement. Traditional method is useful in the measurement of single MZ modulators, but not accurate in that of IQ modulators. In this paper, a novel and effective ER measurement scheme for SiPh IQ-modulator is proposed, and investigated theoretically and experimentally. Compared to the convention method, our algorithm is still robust in SiPh modulator with extinction ratio larger than 45 dB, when the other child MZM is non-ideal and other noise exists. The well repeatability of the proposed algorithm is also demonstrated. The new ER measurement will be very useful in the wafer-level/chip-lever testing to increase the yield.
The wafer-level co-test of optical and analog chips is demonstrated to be cost-cutting solution for coherent optical device packaging. The extinction ratio test and the phase error test are illustrated for example.
In recent years, silicon photonics (SiPh) has generated considerable research interest and achieved rapid progress in coherent optical transceivers market. Automatic bias control (ABC) is an important technology of dual parallel Mach-Zehnder (MZ) optical modulators. Most researches have been investigated based on LiNO3 modulator, but few on SiPh, in which many ABC algorithms become invalid due to the non-idealities. In this paper, a novel and effective ABC scheme for SiPh in-phase and quadrature (IQ) modulator is proposed, and investigated theoretically and experimentally. Compared to the convention method of LiNO3, our algorithm is still robust in SiPh modulator with finite extinction ratios.
It is found that enhancing the coupling between the input or output tapers can cancel the intrinsic imbalance of a 2×2 multimode interferometer (MMI). Furthermore, a highly balanced 2×2 MMI is demonstrated with imbalance less than 0.1 dB in the full C-band by introducing a design with tilted tapers.
We present a 400G chip level Integrated Coherent Receiver optical-electronic testing system. The testing system shows high repeatability and high accuracy compared with commercial device testing system. Besides, we also achieve Graphical User Interface automated testing based on the system, which is high-efficiency for screening qualified chips or devices.
In this study, GaN-based flip-chip parallel micro light-emitting diode (μLED) arrays have been fabricated. Compared to a single LED with the same active region area, flip-chip parallel μLED arrays are superior on both modulation bandwidth and light output because of the uniform current spreading, improved heat dissipation, and higher light extraction efficiency. With this structure, an injected current density up to 7900 A/cm2 has been achieved with a modulation bandwidth of ∼227 MHz. Meanwhile, the optical power is above 30 mW, which is more suitable for visible light communication in free space. The influence of resistance-capacitance (RC) time constant and carrier lifetime on the modulation bandwidth of parallel μLED arrays has also been investigated in details. This study will help the design of GaN-based LEDs to both enhance the modulation bandwidth and optical power.
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