The rapid advancement in integrated optics offers a viable approach for further reducing the size and weight of interferometric fiber optic gyroscopes (IFOGs) by integrating optoelectronic transceiver modules. This paper proposes a design for an integrated optoelectronic transceiver module for IFOG, incorporating a superluminescent laser diode (SLD) light source, beam splitter, photodetector (PD), and transimpedance amplifier (TIA). Through optimization of the optical path and structural design, the emitted optical power from the fiber pigtail exceeded 1 mW under a 100 mA drive current, with the closed-loop overall loss measured at approximately 13 dB. An integrated IFOG test system was developed, and its zero-bias stability was measured at 0.3755 °/h, meeting the requirements of tactical-grade systems. The transceiver shows substantial potential to streamline the IFOG assembly process and reduce assembly costs, a critical factor in the miniaturization of IFOGs.
Chaotic optical communications provide high security for physical layer encryption. We propose a chaotic laser communication system based on a balanced detection optoelectronic delayed feedback system, which has a higher performance compared with one based on single-photodiode detection. Our numerical analysis proves that dynamic behaviors are achieved at only half feedback gain, and the safety hazard chaotic dead zone is eliminated. The generated chaos features high pseudo-randomness and a good capacity to conceal time-delay signatures, which makes it hard for an unauthorized party to remove the chaotic carriers. 10 Gbps message hidden in wideband chaotic carries is transmitted back-to-back, and the BER 10−1 of the eavesdropper achieved at a low feedback gain β=3.2 proves its high confidentiality. Our proposed system has the potential to promote chaotic laser systems to practical appliances with simple structure and high performance.
The performance of a space downlink chaotic laser communication system based on PAM4 modulation under the influence of atmospheric turbulence is studied. Due to the optical intensity scintillation caused by atmospheric turbulence, additional mismatch noise is generated in this communication system. The ensemble average symbol error rate (SER) formula for PAM4 modulation is derived, based on which the performance is studied by numerical simulation. The results show that the ensemble average mismatch noise caused by delay time mismatch is approximately two orders of magnitude larger than that caused by high-frequency cutoff time mismatch and modulator phase mismatch. For PAM4 communication systems under atmospheric turbulence, the communication performance deterioration caused by internal mismatch dominates. Then, the communication performance at higher data baud rates is investigated. As the data baud rate increases, the impact of internal and external mismatch compensation on system performance improvement gradually decreases. At last, the communication performance with PAM8 modulation is discussed as well, and the SER is lower than 10-4 when transmit power is 10 W. This paper has certain reference significance for the parameter design of multi-level modulation space chaos communication system.
To evaluate the effect of crosstalk caused by wavelength deviation of reconstruction-equivalent-chirp (REC) integrated multi-wavelength laser arrays (MWLAs) on an optical free-space communication system in which wavelength division multiplexing (WDM) is applied, we derive the model of power penalty caused by the wavelength deviation of REC-MWLAs and the bit error rate (BER) of the system under atmospheric turbulence and conduct a numerical simulation. The two adjacent channels in arranged REC laser arrays are defined as the analysis scope. We find that the power penalty is more sensitive to the deviation of the channel itself than the adjacent channel as the frequency shift increases from 0 to 50 GHz. The numerical relationship between the BER and power penalty is drawn to further investigate the tolerance for wavelength deviation under the requirements of BER < 10 − 6 and BER < 10 − 9. In addition, for a smaller deviation of 5 GHz of the analyzed channel, the linewidth compression of the REC laser can decrease the power penalty from 1.3 to 0.7 dB, improving the system performance and moderating the demands for deviation of REC-MWLAs, and the gemination of channel spacing does not evidently reduce the requirement for deviation. The results of this work demonstrate the feasibility of REC-MWLAs as the light source of WDM free-space communication systems under atmospheric turbulence and provide an effective reference for the allowable deviation in the design and testing of MWLAs.
KEYWORDS: Waveguides, Distributed feedback semiconductor lasers, Design and modelling, Continuous wave operation, High power lasers, Laser development, Semiconductor lasers, Optical simulations, Near field
In this paper, we designed a Slab Coupled Optical Waveguide (SCOW) DFB semiconductor laser around 1550 nm with increased output optical power and single mode operation. Under the assumption of idea heat dissipation, we simulate the performances of the designed DFB laser using PICs3D software. A Continuous-Wave (CW) output power of 1.03 W is obtained under the bias current of 2.7A, with the slope efficiency of 0.402 W/A. Because of the asymmetric Separated Confinement Heterostructure (SCH) and the passive waveguide structure, the mode profile is expanded. Then, single mode outputs with near-field mode spot size of 5 μm×5 μm and the Full Width at Half Maximum (FWHM) far-field divergence angle is as low as 9.2°×16.2°. Therefore, the designed 1550 nm high power DFB semiconductor laser has potential applications in the fields such as silicon-based photonics integration, Free Space Optical (FSO) communication and light detection and ranging (LiDAR) systems.
All-optical switches have the advantage of significantly reducing the cost of data-center and improving the transmission characteristics of the system, which has led to many different optical switching technologies for data-center. For this application, we demonstrate a superfast wavelength switching drive design for DFB laser array, and realize a fast tunable laser with 5 ns switching latency. The laser array (C-band, 16-channel, 100 G-space) we used is based on the reconstructed equivalent chirp technology. During the process of tuning, the output wavelength of each channel is within the channel wavelength error range specified by DWDM under the ITU-T standard. Based on the above light source, we build a complete prototype of all-optical switching transceiver integrating transceiver and transmitter, and demonstrate the stable transmission of 10.24 Gb/s data under the condition of four wavelength arbitrary switching and routing.
Quadrature Phase Shift Keying (QPSK) is an important digital signal modulation method, which has the advantages of high spectrum efficiency and strong anti-interference. Coherent laser communication has the advantages of high speed, large capacity, light and small equipment as well as high sensitivity. In order to better introduce the QPSK modulation method into the space downlink coherent laser communication system, we give a bit error rate (BER) of QPSK modulation model with laser linewidth suitable for space downlink coherent laser communication system with QPSK modulation under atmospheric turbulence. Based on the model, we simulate and analyze the effects of atmospheric wind speed, zenith angle, gain of Erbium doped optical fiber amplifier (EDFA) and communication rate on the linewidth tolerance of space downlink coherent laser communication system with QPSK modulation. The results show that the linewidth tolerance of the system increases when the zenith angle decreases or the gain of EDFA increases or the wind speed decreases. And the effects of zenith angle, gain of EDFA and communication rate on the linewidth tolerance of the space downlink coherent laser communication system with QPSK modulation are large. The effect of wind speed on the linewidth tolerance of space downlink coherent laser communication system with QPSK modulation is smaller. And the larger the wind speed is, the smaller the effect of increasing wind speed on the linewidth tolerance. For the communication rate, the linewidth tolerance increases and then decreases with the increase of the communication rate. This work can be a reference for the design of space downlink coherent laser communication system with QPSK modulation.
In order to investigate the influence of different system parameters on linewidth tolerance in space coherent optical communication system, we give the ensemble average bit error rate (BER) model of binary phase-shift keying (BPSK) modulation and homodyne detection space coherent optical communication system. The BER model also considers the laser linewidth induced phase noise and pointing error. Based on the BER model, the numerical simulation is conducted to investigate the relationship between linewidth tolerance and different system parameters of divergence angle, receiving aperture, zenith angle, and transmitted optical power. Through our numerical simulation, it is found that the linewidth tolerance will change from several kHz to several hundred kHz. Besides, linewidth tolerance will decrease with the increase of divergence angle and zenith angle. While with the increase of receiving aperture and transmitted optical power, the linewidth tolerance will increase. Also, we find that the linewidth tolerance changes more obviously with the variation of the zenith angle. This paper has a good reference value for the selection of laser linewidth of the space coherent optical communication system under different system parameters.
Atmospheric intensity scintillation effect deteriorates the communication quality of space chaos laser communication. To analyze the effect of internal mismatch and internal mismatch induced by intensity scintillation on bit error rate (BER) for space downlink chaos laser communication system, numerical simulation results based on BER formula are conducted and analyzed. Numerical results demonstrate that BER worsens with the effect of intensity scintillation. Although the probability that received optical power causes larger mismatch noises is small, its corresponding larger instantaneous BER deteriorates the ensemble average BER significantly. Results also indicate that internal mismatch deteriorates BER more than external mismatch. These results are beneficial for designing practical space chaos laser communication system with optimal performance.
The application of Golay pulse coding technique on Brillouin optical time-domain reflectometer (BOTDR) in a radiation environment is experimentally analyzed. By applying Golay pulse codes on the BOTDR system in the radiation experiment, the enhancement of detection range, accuracy of Brillouin frequency shift (BFS), and reduction of stress measurement error are characterized. By using 64-bit Golay coding, signal-to-noise ratio can be improved significantly and the variation of BFS is more accurate. These results are beneficial for the application of the Golay pulse code technique on BOTDR in the space station.
Chaotic optical communication is a secure communication method which uses synchronous chaotic carrier to realize encryption and decryption. With the demand for information security increasing, chaotic encryption has been applied to space optical communication experimentally. However, due to the complexity of chaotic system design, the bit error rate (BER) of space chaotic optical communication system is much higher than that of traditional one. High BER limits the bitrate of space chaotic optical communication while bitrate is quite important since a large amount of information needs to be transmitted in space downlink. According to our previous work, introducing two diffractive optical elements (DOEs) into optical subsystem can improve transmission efficiency, which equals to increasing transmission power. In this manuscript, we further investigate the effect of DOEs on BER and propose some suggestions on BER enhancement of space downlink chaotic optical communication.
We present a tunable experimental setup to obtain the three-dimensional refractive index distribution of microscopic biological structures. We introduce an adjustable system to change the position of the focal plane and perform stitched reconstruction. There are two main approaches for obtaining the projections of sample in optical diffraction tomography: beam scanning and rotating sample. Compared to beam scanning, the method of rotating sample allows the sample to be rotated 180° to capture uniformly distributed data, which improves the accuracy of the phase measurement and the resolution of the reconstruction result. The depth-of-field in the optical diffraction tomography setups is very small and the method of rotating sample inevitably causes the sample to deviate from the depth-of-field during the rotation, making it difficult to obtain ideal data. We divided the sample position deviation area into several ideal data acquisition areas and collected the ideal data in each area by shifting the position of the focal plane. By the combination of 180° projection method and stitched reconstruction method, we have obtained high measurement accuracy results with uniform resolution.
In recent years, with the development of eavesdropping technology, how to improve the security of data transmission has become a hot research issue. In order to enhance the security of the secure communication system, a chaotic laser secure communication system with variable laser power is proposed in this paper. Based on the original optoelectronic feedback chaotic laser communication system, the change of laser power is regarded as a new key. The simulation results show that the error rate of the eavesdropper is above 10-2 over most of the laser power, and the average error bit rate of the eavesdropper is 7 orders of magnitude higher than the average error rate of the authorized receiver. In addition, the appropriate masking efficiency will reduce the bit error rate of the eavesdropper, while it has little effect on the eavesdropper. The system scheme can be used in communication with high confidentiality requirements in the future.
Brillouin Optical Time Domain Reflectometer (BOTDR), as a distributed optical fiber sensing technique, has been widely used in health monitoring of large structures on the ground in recent years. Space engineers also have a strong interest in it. However, in space environment, the optical performance of sensing fibers in BOTDR will decrease due to space radiation. Usually, the ground simulation space radiation experiment only considers the influence of radiation damage on optical properties of optical fibers. However, the performance variation of optical fibers after radiation is a combined result of radiation damage and self-recovery. If the restoring characteristic is introduced into the radiation damage model, the accuracy of BOTDR radiation assessment will be greatly improved. To study the radiation recovery characteristics of BOTDR, a 1 km single-mode G.652.D YOFC fiber is used as the sensing optical fiber of BOTDR, and is placed in the radiation field of Co 60 to receive 200Gy gamma radiation with 1.42 Gy/min dose rate. After the radiation procedure, the radiation recovery characteristics of BOTDR were monitored for 1506 hours. The experimental results show that the radiation recovery effect has little effect on Brillouin frequency shift and stress coefficient, but the attenuation coefficient of optical fiber caused by radiation can be restored obviously in the first 100 hours. The attenuation coefficient of optical fiber recovers from 3.5 dB/km to 1.5 dB/km. The above results are of great significance to modify the radiation model of BOTDR in space radiation environment.
When optical chaos communication system is applied to space optical communication, some necessary structural modifications are needed, and atmospheric effects are required to be considered. As one of these effects, beam spreading can affect the bit error rate (BER) of space optical chaos communication system under nonzero detector mismatch. To study the specific effect of beam spreading on the system BER, we make a formula modification including this effect. And based on the derived formula, we conduct a numerical simulation of the system BER under different detector mismatches. In our numerical simulation, we select the five typical system parameters of such system, which are synchronization error, zenith angle, transmitting power, divergence angle, and receiving diameter, and obtain their relationships with the BER. Corresponding discussions are made according to our results, which are beneficial to practical application of space optical chaos communication system.
Numerous communication techniques and optical devices successfully applied in space optical communication system indicates a good portability of it. With this good portability, typical coherent demodulation technique of Costas loop can be easily adopted in space optical communication system. As one of the components of pointing error, the effect of jitter plays an important role in the communication quality of such system. Here, we obtain the probability density functions (PDF) of different jitter degrees and explain their essential effect on the bit error rate (BER) space optical communication system. Also, under the effect of jitter, we research the bit error rate of space coherent optical communication system using Costas loop with different system parameters of transmission power, divergence angle, receiving diameter, avalanche photodiode (APD) gain, and phase deviation caused by Costas loop. Through a numerical simulation of this kind of communication system, we demonstrate the relationship between the BER and these system parameters, and some corresponding methods of system optimization are presented to enhance the communication quality.
Based on electromagnetic eigenequation in silver-coated microcylinder, we study its mode characteristics and sensing characteristics, including dispersion relation, quality factor (Q factor), sensitivity (S) and detection limit (DL). We find hybrid WGM-SPPs modes in energy distribution and mode coupling phenomenon in dispersion curve. In the vicinity of mode coupling point, hybrid TM-SPPs modes (or supermodes) have both high Q factor and high surface enhancement factor. Meanwhile the hybrid modes have high refractive sensitivity and figure of merit (FoM), which enables potential applications in chemical and biological sensing.
Based on weak fluctuation theory, the expression of bit-error rate (BER) of Multiple Quadrature Amplitude Modulation (MQAM) with the consideration of detector noise in the downlink of space communication system is discussed in this paper. According to the expression, the performance of three typical modulation schemes, which are 4QAM, 16QAM, 64QAM, are specially analyzed. It is known that the higher the order of the modulation scheme is, the more bits of information per symbol can carry. However, when the transmission power is 1 W and the receiver diameter Dr is 1 m, the BER is 2.12×10-13 for 4QAM, 5.98×10-8 for 16QAM and 6.22×10-5 for 64QAM, which means that a higher order modulation scheme shows a higher bit-error rate (BER). Thus considering bandwidth efficiency as well as bit error rate, 16QAM is highly recommended in the real space optical communication system. In addition, the relationships between BER and optimum divergence angle, transmitter beam radius, receiving aperture for downlink are also suggested respectively in this paper, which has important reference significance for the design of the ground-to-satellite laser communication system.
Space optical communication technique is attracting increasingly more attention because it owns advantages such as high security and great communication quality compared with microwave communication. As the space optical communication develops, people have already achieved the communication at data rate of Gb/s currently. The next generation for space optical system have goal of the higher data rate of 40Gb/s. However, the traditional optical communication system cannot satisfy it when the data rate of system is at such high extent. This paper will introduce ground optical communication system of 40Gb/s data rate as to achieve the space optical communication at high data rate. Speaking of the data rate of 40Gb/s, we must apply waveguide modulator to modulate the optical signal and magnify this signal by laser amplifier. Moreover, the more sensitive avalanche photodiode (APD) will be as the detector to increase the communication quality. Based on communication system above, we analyze character of communication quality in downlink of space optical communication system when data rate is at the level of 40Gb/s. The bit error rate (BER) performance, an important factor to justify communication quality, versus some parameter ratios is discussed. From results, there exists optimum ratio of gain factor and divergence angle, which shows the best BER performance. We can also increase ratio of receiving diameter and divergence angle for better communication quality. These results can be helpful to comprehend the character of optical communication system at high data rate and contribute to the system design.
For a space downlink laser communication system with an EDFA as a power amplifier, the
performance of its BER deteriorates because the EDFA’s characteristics are badly impacted by space
radiation. As is investigated in this paper, small divergence-angle, lower than 30μrad, assures that the
BER is lower than10-20 although the increase of radiation dose from 0Gy to 250Gy leads to 20 orders of
magnitude increase of the BER. Such perfection results from our selection of optimal parameters. In
the case of zenith angle, the BER increases smoothly when the zenith angle is lower than 10 degrees.
After the point of 10 degrees, however, the BER starts its linearly fast increase. Increasing the radiation
dose makes the BER increase and such evolution trend more smooth. Moreover, the increase of
receiving diameter leads to linear reduce of BER. It is interesting to note that the evolution becomes
nonlinear in region of low receiving diameter when we change the divergence-angle to a higher value
60μrad. Besides, suffering radiation makes the non-linearity mentioned above more apparent. Another
try to change the zenith angle to higher value 45° does not show obvious nonlinear effect but it worsens
the performance of BER quite a lot. Commonly, the impact of radiation will reach its saturation when
the dose of radiation continues to increase. The work will benefit the design of practical space laser
communication system with EDFAs.
The erbium doped fiber, optical isolator and WDM coupler, which are three key optical components of commercial
erbium-doped fiber amplifier (EDFA), are radiated to the radiation dose of 5krad by electron. The radiated erbium-doped
fiber (EDF) make the output power of EDFA come down 0.5dB when the input power is between -12dBm and-5dBm.
The NF climb up 1dB. However, the peak wavelength changes little. The radiation experiment results also show that the
deterioration of the optical isolator and WDM coupler can be neglected at the dose of 5krad. In order to assure the
accuracy of analysis, the recovery experiment has been done to correct the radiation effect on the EDFA. The results
indicate that if optical communication systems have enough redundancy, the EDFA can be used on the low dose orbits
without any radiation protection for inter-satellite optical communication.
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