US 12,081,319 B2
Optical transmitter
Andrea C. Ferrari, Cambridge (GB); Marco Romagnoli, Milan (IT); and Vito Sorianello, San Giuliano Terme (IT)
Assigned to Cambridge Enterprise Limited, (GB); and Consorzio Nazionale Interuniversitario per le Telecomunicazione, (IT)
Appl. No. 17/436,570
Filed by Cambridge Enterprise Limited, Cambridge (GB); and Consorzio Nazionale Interuniversitario per le Telecomunicazioni (CNIT), Parma (IT)
PCT Filed Feb. 27, 2020, PCT No. PCT/GB2020/050476
§ 371(c)(1), (2) Date Sep. 3, 2021,
PCT Pub. No. WO2020/178559, PCT Pub. Date Sep. 10, 2020.
Claims priority of application No. 1902970 (GB), filed on Mar. 6, 2019.
Prior Publication US 2022/0149967 A1, May 12, 2022
Int. Cl. H04J 14/02 (2006.01); H04B 10/2513 (2013.01); H04B 10/548 (2013.01)
CPC H04J 14/02 (2013.01) [H04B 10/25137 (2013.01); H04B 10/548 (2013.01)] 20 Claims
OG exemplary drawing
 
1. A Wavelength Division Multiplexing (WDM) optical transmitter for transmitting a WDM signal along an optical fibre, the WDM optical transmitter comprising:
a set of optical inputs, one for each wavelength of a WDM optical signal to be transmitted;
a graphene electro-absorption modulator (EAM) for each optical input to modulate light from the optical input; and
one or more drivers to drive each graphene electro-absorption modulator,
wherein the one or more drivers have a data input, a low pass filter to low-pass filter data from the data input to provide low pass filtered data, and an output to drive each graphene electro-absorption modulator with a combination of the low pass filtered data and a bias voltage configured to bias the graphene electro-absorption modulator into a region in which when the transmission of the graphene electro-absorption modulator changes in a first direction the effective refractive index for the modulated light changes in a second, opposite direction and vice-versa,
to provide a chirp having a first sign to the modulated light to compensate for a chirp having a second, opposite sign due to transmission of the modulated light through the optical fibre; and
wherein the one or more drivers are configured to drive the graphene electro-absorption modulators for different wavelengths with different drive voltages to provide a different positive pre-chirp to the modulated light at different wavelengths to match changes in dispersion in the optical fibre with wavelength.