Photonic balancing - a scheme where logically opposite pulses derived from the two outputs of a delay-line demodulator
for phase shift keyed (PSK) signals counter-propagate in the saturated regime of a semiconductor optical amplifier
(SOA) - has been proven to enhance the receiver performance, e.g. in terms of decreased optical signal-to-noise-ratio
(OSNR) requirements for a given target bit error ratio (BER). Here, we extend the photonic balancing scheme towards a
new concept for a regenerative amplifier targeted at extending the reach and/or the number of subscribers in passive
optical networks (PON) in order to support major operators' plans to reduce the number of central offices and access
areas by approximately 90%. For a given target BER, we demonstrate experimentally (a) an 8-dB higher post-amplifier
loss tolerance, (b) an extended feeder line length (75 km) combined with high splitting ratio (10 layers) for a preamplified
version, and (c) high input power variation tolerance (> 30 dB burst-to-burst) in upstream direction as needed
for highly asymmetric tree structures.
A nonlinear optical loop mirror with a bidirectional attenuator has been used for regeneration of return-to-zero
differential phase-shift-keyed (RZ-DPSK) signals. A 2.5 ps, 10 Gb/s signal with amplitude fluctuations of 28 % was
regenerated with a negative power penalty of 2 dB practically back to the quality of the undistorted reference signal.
Parameters limiting system performance and optimization possibilities will be discussed.
We present an optical receiver for RZ-DPSK signals that use photonic balancing. Photonic balancing is achieved through
pulse counter-propagation and collision in a saturated SOA. We explain the principles of photonic balancing and show
how it can lead to an improvement in RZ-DPSK detection by 3 dB, similar to electrical balancing. We also show how
this scheme can be used as a Mamyshev-type regenerator.
Sophisticated modulation formats like phase shift keying (PSK) as discussed for high-speed fiber-optic transmission systems operating at 40 Gbit/s and beyond, cause new challenges for clock recovery. Whereas conventional return-to-zero on-off keyed (RZ-OOK) modulated signals provide proper clock tones which can be used to recover the clock signal, the additional phase modulation (RZ-PSK) changes the spectral composition of the signal and weakens or suppresses the clock tones. This effect is bit pattern dependent as can be seen from a simple example: If all the pulses in an RZ-PSK signal are in phase, the result is equivalent to an ordinary RZ on-off-keying (OOK) signal with a strong carrier and clock tones. If the pulses in a sequence oscillate in phase by &pgr;, the result is equivalent to the well-known carrier-suppressed return-to-zero signal (CS-RZ) where the carrier is suppressed and where clock tones are differently spaced compared to RZ-OOK. In this paper we present results of the simulation of the different cases taking into account realistic bit sequences and analyze the results with special emphasis on the influence the effect has on clock recovery.
A new fiber sensor integrated monitor to be used in an embedded instrumentation system is proposed and its operating features are examined. The system integrates a fiber sensor together with a tunable MEMS filter, superluminescent light emitting diode and microcontroller creating a high-speed, low cost, low power smart sensor. The device has applications to a variety of fiber sensing technologies and, as an example, is integrated with a fiber Bragg grating for temperature sensing.