Laser diode used in 16 Mb/s, 10 mW optical transcutaneous telemetry system

Abstract

Developments in neuroprosthetics have lead to applications with high channel counts, thus increasing the need for high bandwidth telemetry systems to transmit data out of the body. Optical telemetry is a promising implantable telemetry solution, and data rates and power consumption criteria are being established. This paper presents the performance of a laser diode-based system in various operating conditions. This system transmits at data rates up to 16 Mb/s through a skin thickness of 4 mm while achieving a BER of 1E-9 with consumption of 10 mW or less.

Emerging Optical Wireless Communications-Advances and Challenges

“…The medical window or the therapeutic window is in the nearinfrared spectrum between 650 to 950 nm where light has its maximum depth of penetration through the skin [71,74,77]. At lower and upper wavelengths scattering and absorption by water and blood components is higher.…”

Transdermal Optical Wireless Links with Multiple Receivers in the Presence of Skin-Induced Attenuation and Pointing Errors

“…Additionally, many commercially available emitters and photodiodes are optimized for operation in skin's 'optical window' range, as is the same wavelength range used for many fiber optics or free-air applications [32]. Nevertheless, this skin-induced attenuation described above remains a major concern in TOW communication since even for the highest tissue transmittance, i.e., for wavelengths between 800 nm and 1300 nm, only 10% to 30% of incident optical power is transmitted through skin of typical thickness, i.e., 2 mm to 6 mm, when the emitter and the detector are aligned [33][34][35]. Considering also the pointing errors due to unavoidable misalignments between transmitter and receiver terminals that is also an effect of primary concern in TOW communication, as well as in the wider FSO communication, the performance and availability of TOW transmissions is further degraded [2,4,7,[36][37][38][39].…”

“…Next, in [14] the concept of a "Medical Spectral Window", commonly known as skin's'optical window' mentioned above, has been experimentally proven. Within this wavelength region, optical radiation is least attenuated traversing human skin, and therefore, the propagating light experiences its maximum depth of penetration, penetrating into tissue as much as several centimeters [14,30,32,33,35]. Additionally, by using a vertical cavity surface emitting laser (VCSEL) with 850 nm wavelength very effective TOW experimental links have been reported in [19,29,35].…”

“…Within this wavelength region, optical radiation is least attenuated traversing human skin, and therefore, the propagating light experiences its maximum depth of penetration, penetrating into tissue as much as several centimeters [14,30,32,33,35]. Additionally, by using a vertical cavity surface emitting laser (VCSEL) with 850 nm wavelength very effective TOW experimental links have been reported in [19,29,35]. More precisely, in [35], data rates up to 16 Mbps have been achieved through a skin thickness of 4 mm with a bit error rate (BER) of order of 10 −9 and misalignment between transmitter and receiver terminals of 2 mm, while consuming a power of 10 mW.…”

“…Additionally, by using a vertical cavity surface emitting laser (VCSEL) with 850 nm wavelength very effective TOW experimental links have been reported in [19,29,35]. More precisely, in [35], data rates up to 16 Mbps have been achieved through a skin thickness of 4 mm with a bit error rate (BER) of order of 10 −9 and misalignment between transmitter and receiver terminals of 2 mm, while consuming a power of 10 mW. In [19], a TOW link capable of transmitting data at 50 Mbps through sufficiently thick tissue, i.e., 2-6 mm, with a BER below 1 × 10 −5 and power consumption as low as 1.1 mW to 6.4 mW respectively, considering 2 mm misalignment between terminals, while in [29] in vivo tests performed on an anesthetized sheep demonstrated transmitting data at 100 Mbps with a BER below 2 × 10 −7 , consuming only 2.1 mW of electrical power.…”