Minimum Channel Spacing Research Articles

Angle-tuned etalon filters for optical channel selection in high density wavelength division multiplexed systems

Applications are discussed for angle-tuned in-line Fabry-Perot etalons for optical channel selection in a high-density wavelength division multiplexed (WDM) direct-detection fiber system. A typical WDM application (LAMBDANET type) was described. Different demultiplexing techniques and their relative advantages were considered. Design guidelines are given for determining the etalon parameters, the minimum channel spacing and the maximum number of channels for a single etalon and multiple etalons, including stacked identical etalons and stacked nonidentical etalons. Experimental results on using these etalons for optical channel tuning in a multiwavelength WDM optical communication system are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Crosstalk penalty in multichannel ASK heterodyne lightwave systems

The author addresses the issue of optimum channel spacing in multichannel amplitude-shift-keying (ASK) heterodyne lightwave systems by considering the bit-error-rate (BER) degradation resulting from interchannel crosstalk. An expression for the BER of a specific channel is obtained by considering the crosstalk from both of its nearest neighbors. The general result is used to calculate the power penalty as a function of the crosstalk level. The crosstalk is shown to depend on a large number of system parameters, such as the bit rates, the received powers, the channel spacing, and the response of the bandpass filter. For the case of equal bit rates and equal received powers in all channels, the crosstalk from each channel should be below -12 dB to keep the power penalty below 1 dB, which means a minimum channel spacing of about four or five times the bit rate. If the objective is to reduce the power penalty below 0.1 dB, the interchannel crosstalk should be less than -18 dB, which would require a minimum channel spacing of about ten times the bit rate.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

FDMA-FSK star network with a tunable optical filter demultiplexer

An optical frequency-division-multiple-access (FDMA) star network is analyzed and demonstrated experimentally using two 45-Mb/s frequency-shift-keyed (FSK) laser channels at 1.5 mu m. A tunable fiber Fabry-Perot (FFP) filter is used to select channels and convert FSK to intensity modulation for direct detection. The analysis predicts and experiment supports a minimum channel spacing of about six times bit rate B for a single FFP. These constraints are similar to those for more complex heterodyne demultiplexing. Estimates show that a network with 1000 users, independent of bit rate, is feasible with a tandem FFP. For B=1 Gb/s per channel the network capacity would be 1 Tb/s.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Network experiment using an 8000 GHz tuning-range optical filter

A tunable optical filter with 180 MHz resolution and continuous tuning range of 8000 GHz was used in a lightwave network experiment. Three 50Mbit/s channels with minimum channel spacing of 1.6 GHz and maximum channel pacing of 4000 GHz were individually received error-free in the presence of interfering optical power corresponding to 6000 channels.

Evaluation of crosstalk penalty in multichannel ASK heterodyne optical communication systems

The bit error rate (BER) of a two-channel ASK heterodyne lightwave system employing envelope detection is evaluated analytically. The result is used to calculate the power penalty resulting from intrachannel crosstalk. To main a BER below 10−9, the power penalty increases from 0.2 to 1 dB when the level of crosstalk increases from −15 to −10 dB. The theory predicts a minimum channel spacing of three times the bit rate if the design criterion is to keep the crosstalk penalty below 0.1 dB. The minimum channel spacing increases to five times the bit rate for multichannel systems when crosstalk from the nearest neighbours on both sides is included.

FDM-FSK star network with a tunable optical filter demultiplexer

An optical frequency-division-multiplexed star network is analysed and demonstrated experimentally using two 45Mbit/s frequency-shift-keyed laser channels at 1.5 μm. A tunable fibre Fabry-Perot filter is used as demultiplexer. The analysis predicts and experiment supports a minimum channel spacing of about six times bit rate B for a single FFP and 3B for a tandem FFP.

A minimum channel spacing of optical wavelength‐division‐multiplexing transsion for subscriber loop systems

AbstractThis paper describes standardization of wavelengths in wavelength‐division‐multiplexing transmission for optical subscriber loop systems. First we estimate the minimum channel spacing for both the short and long wavelength regions considering such system requirements as transmission distance, transmission signals and future trend of optical components (e.g., optical source, optical multi/demultiplexer, optical connector and optical fiber) and select eight wavelengths in the short wavelength region (0.75, 0.77, 0.79, 0.81, 0.83, 0.85, 0.87 and 0.89 μm) and eight wavelengths in the long wavelength region (1.10, 1.15, 1.20, 1.25, 1.30, 1.35, 1.40 and 1.45 μm). Then, considering presently required transmission signals and the present state of the art of optical sources and optical components, it is concluded that the use of two wavelengths in the short wavelength region (0.81 and 0.89 μm) and two in the long wavelength region (1.2 and 1.3 μm) will suffice for the time being, and that with the required technological advances, necessary wavelengths will be developed and used from among the 16 wavelengths.