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METHOD AND SYSTEM FOR REDUCING THE IMPACT OF OPTICAL TRANSMITTER TUNING TIME FOR OPTICAL SERVICE ADDITIONS AND MESH RESTORATION

IP.com Disclosure Number: IPCOM000247068D
Publication Date: 2016-Aug-01
Document File: 7 page(s) / 773K

Publishing Venue

The IP.com Prior Art Database

Abstract

In various exemplary embodiments, the present disclosure reduces the impact of optical transmitter (Tx) tuning such as in optical networks using coherent modulation. The impact of Tx tuning time in layer 0 restoration is significant due to the sequential dependence of Tx tuning completion and the photonic switching activities over the Optical Add/Drop Multiplexer (OADM) nodes. This disclosure reduces the impact of Tx tuning time on mesh restoration or in regular service addition phase by overlapping the Tx tuning/retuning time and photonic switching time instead of sequencing them, where the overlapping is achieved by generating a makeshift optical signal (curved Amplified Stimulated Emission (ASE), or unmodulated signal) from the Tx circuit pack on the desired frequency. Such an approached can be achieved using existing capabilities of a typical Tx circuit pack or line module, without introducing any new photonic circuit packs per OADM sections in the photonic line system.

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    METHOD AND SYSTEM FOR REDUCING THE IMPACT OF OPTICAL TRANSMITTER TUNING TIME FOR OPTICAL SERVICE ADDITIONS AND MESH RESTORATION

ABSTRACT


[0001]In various exemplary embodiments, the present disclosure reduces the impact of optical transmitter (Tx) tuning such as in optical networks using coherent modulation. The impact of Tx tuning time in layer 0 restoration is significant due to the sequential dependence of Tx tuning completion and the photonic switching activities over the Optical Add/Drop Multiplexer (OADM) nodes. This disclosure reduces the impact of Tx tuning time on mesh restoration or in regular service addition phase by overlapping the Tx tuning/retuning time and photonic switching time instead of sequencing them, where the overlapping is achieved by generating a makeshift optical signal (curved Amplified Stimulated Emission (ASE), or unmodulated signal) from the Tx circuit pack on the desired frequency. Such an approached can be achieved using existing capabilities of a typical Tx circuit pack or line module, without introducing any new photonic circuit packs per OADM sections in the photonic line system.

DESCRIPTION


[0002]Optical networks have moved to coherent modulation supporting capacity of 100Gb/s or more. Turning a coherent optical transmitter on requires tuning time to adjust to line conditions. A high-level functional block diagram view of a typical coherent transmitter/receiver (Tx/Rx) is illustrated in FIG. 1, where to tune the Tx to a particular frequency, the laser is first tuned to that frequency which typically takes few seconds to 10's of seconds based on the laser manufacturers, quality, precision and performance, and its initial starting point. Sweeping the laser from one frequency to another can affect traffic on other frequencies in the spectrum in a colorless multiplexer (mux) environment due to which variable optical attenuator (VOA) or shutter is used to block the light coming out of the Tx port. The optical signal generated by the laser is then passed through an electro-optic (E/O) Tx subsystem that maps the traffic data and modulates the optical signal to a proper baud rate. Setting the modulation on the Tx signal can typically take 10's of seconds, and can create large perturbations on the optical signal power, which is another reason to keep the VOA or the shutter at a block position to ensure no optical signal is coming out of Tx until the laser is fully tuned and modulated to the proper baud rate, and calibrated properly for optimal optical performance. Once the Tx is tuned, a combination of VOA, Erbium Doped Fiber Amplifier (EDFA) and wide-band tunable optical filters are then typically used to present a Tx signal at the Tx port at a specific power target as required by the photonic configurations. Based on performance criteria, the overall Tx tuning process can take from 10's of seconds to minutes, and until then, no photonic switching takes place due to lack of light with expected signal...