SEMICONDUCTOR WAVELENGTH TUNABLE OPTICAL FILTERS

1993 ◽  
Vol 02 (04) ◽  
pp. 643-659 ◽  
Author(s):  
T. NUMAI
Keyword(s):  
Wavelength Division Multiplexing ◽  
Direct Detection ◽  
Optical Filters ◽  
Switching Systems ◽  
Switching Speed ◽  
Photonic Switching ◽  
Detection Scheme ◽  
Wavelength Division ◽  
Wavelength Tunable ◽  
Tunable Optical Filters

Wavelength-division multiplexing (WDM) lightwave transmission systems and wavelength-division (WD) photonic switching systems are attractive for improvement in line capacity for lightwave telecommunication services, because they utilize a huge wavelength (frequency) domain as signal channels. Wavelength tunable optical filters are key devices for these WDM and WD systems in direct detection scheme. In particular, semiconductor wavelength tunable optical filters are suitable for monolithic integration with photonic devices such as semiconductor lasers, switches and detectors. Also, the switching speed of wavelength is faster than that of other optical filters. This paper briefly summarizes the state-of-the-art semiconductor wavelength tunable optical filters and their applications to WD photonic switching systems.

Systematic identification of crosstalk and bandwidth upper limit in highly cascaded Mach-Zehnder lattice optical filters

2021 ◽  
Author(s):  
Jun Ushida ◽  
Tadashi Murao ◽  
Akemi Shiina ◽  
Tsuyoshi Horikawa
Keyword(s):  
Wavelength Division Multiplexing ◽  
Communication Systems ◽  
Direct Detection ◽  
Optical Filter ◽  
Optical Filters ◽  
Coupling Coefficients ◽  
Wafer Level ◽  
Wavelength Division ◽  
Level Measurement ◽  
Upper Limit

Abstract Crosstalk among channels in wavelength division multiplexing (WDM) filters must be suppressed to enhance receiver sensitivity in direct-detection-based optical communication systems. We present a systematic method to identify the maximum crosstalk and upper limit of the transmission spectrum bandwidth of a highly multi-staged Mach-Zehnder interference (MZI) lattice optical filter with a number of cascade N (N=1,2,…,∞). The scattering matrix including the wafer-level-measurement-based coupling coefficients of directional couplers is used to calculate the transmittance from the input to each output channel and the result is exactly extrapolated to infinite N. This method can be used to design, characterize, and evaluate $N$-cascaded MZI lattice optical filters that must meet strict WDM specifications.

scholarly journals Joint Probabilistic-Nyquist Pulse Shaping for an LDPC-Coded 8-PAM Signal in DWDM Data Center Communications

2019 ◽  
Vol 9 (23) ◽  
pp. 4996 ◽  
Author(s):  
Han ◽  
Yang ◽  
Djordjevic ◽  
Yue ◽  
Wang ◽  
...  
Keyword(s):  
Wavelength Division Multiplexing ◽  
Spectral Efficiency ◽  
Data Center ◽  
Pulse Shaping ◽  
Direct Detection ◽  
Signal Transmission ◽  
Ldpc Code ◽  
Pulse Amplitude ◽  
Wavelength Division ◽  
Nyquist Pulse

M-ary pulse-amplitude modulation (PAM) meets the requirements of data center communication because of its simplicity, but coarse entropy granularity cannot meet the dynamic bandwidth demands, and there is a large capacity gap between uniform formats and the Shannon limit. The dense wavelength division multiplexing (DWDM) system is widely used to increase the channel capacity, but low spectral efficiency of the intensity modulation/direct detection (IM/DD) solution restricts the throughput of the modern DWDM data center networks. Probabilistic shaping distribution is a good candidate to offer us a fine entropy granularity and efficiently reduce the gap to the Shannon limit, and Nyquist pulse shaping is widely used to increase the spectral efficiency. We aim toward the joint usage of probabilistic shaping and Nyquist pulse shaping with low-density parity-check (LDPC) coding to improve the bit error rate (BER) performance of 8-PAM signal transmission. We optimized the code rate of the LDPC code and compared different Nyquist pulse shaping parameters using simulations and experiments. We achieved a 0.43 dB gain using Nyquist pulse shaping, and a 1.1 dB gain using probabilistic shaping, while the joint use of probabilistic shaping and Nyquist pulse shaping achieved a 1.27 dB gain, which offers an excellent improvement without upgrading the transceivers.

Study of the Different Optical Filters in SAC-OCDMA System

2018 ◽  
Vol 39 (4) ◽  
pp. 381-386 ◽  
Author(s):  
H. Djellab ◽  
N. Doghmane ◽  
A. Bouarfa ◽  
M. Kandouci
Keyword(s):  
Wavelength Division Multiplexing ◽  
Local Area Network ◽  
Direct Detection ◽  
Optical Filter ◽  
Optical Filters ◽  
Local Area ◽  
Spectral Amplitude ◽  
Area Network ◽  
Code Division Multiple ◽  
The Impact

Abstract Spectral amplitude coding for optical code division multiple access (SAC-OCDMA) networks has received much attention over the last two decades. This article aims to explore the impact of encoder change on different types of optical filters, such as the Gaussian optical filter and the Bessel optical filter, for high data rates and to give an overview on importance of choosing the optimal type of optical filter according to the frequency range selected by the user is 25 and 50 GHz. SAC-OCDMA transmitter utilizes Wavelength Division Multiplexing multiplexer (WDM MUX) as an encoder, to generate a code having low cross-correlation called Random Diagonal code, and spectral direct detection as a detection technique. The change of optical filter, in WDM MUX, directly affects the performance of the system. The results show that the system for 50 GHz, with a WDM MUX, using a Gaussian optical filter has better performance compared to the optical Bessel filter and can reach a bit error rate (BER) of 10−25. SAC-OCDMA system, using a WDM MUX based on Bessel filters with a bit rate of 300Mb/s, achieves a BER of 10−28 which leads us to recommend it for second norm 25 GHz. Moreover, the power received increases by 4 dBm every 20 Km with the increase in the length of the fibre for both filters Bessel and Gaussian. Our work focuses on the two 25 and 50 GHz bands, after a study on the impact of the change of the bandwidth and the order of the different optical filters used according to the BER applied to the different networks of access, such as local area network (LAN).

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