From the architecture diagram, the optical access network
comprises the following scenarios:
1. FTTB scenario
2. FTTC & FTTCab scenario
3. FTTH scenario
• Fiber to the Building , is the deployment of fiber (optical)
cable to a specific location within a building, then
connected to the buildings existing copper cable facilities.
• This deployment is also referred to as :
i. FTTB (Fiber to the Basement)
ii. FTTB (Fiber to the Business).
• This deployment will be the typical for MTU’s.
i. MTU :Business Multi-tenant unit ; providing a comparatively larger number
of ports, including POTS, 10/100/1000BASE-T and DS1/T1/E1 ports.
• Fiber to the Curb , is the deployment of fiber close to the
customer but not fully to the customers residence.
i. MDU : Multi-dwelling unit ;providing a comparatively larger number of ports,
including 10/100/1000BASE-T, VDSL2, and so on.
• In this deployment the existing copper plant is still used to
deliver service to the actual customer.
• Following Scenarios Also Falls Under This Category
i. FTTN (Fiber to the Neighborhood)
ii. FTTC (Fiber to the Cabinet)
• Fiber to the Home is the complete deployment of fiber
to the customers home, with replacement of there
existing NID (Network Interface Device).
i. SFU : Single family unit , providing a comparatively small number of ports,
including following types: POTS, 10/100/1000BASE-T, and RF.
• This replacement device is called an ONT (Optical
i. The ONT converts fiber-optic light signals to copper/electric signals.
• A passive optical network (PON) is a point-to-multipoint,
fiber to the premises (FTTP) network architecture in which
unpowered optical splitters are used to enable a single
optical fiber to serve multiple premises
• In Simple it uses passive optical splitters to serve many
subscribers from one optical unit
• A PON consists of
i. Optical Line Terminal (OLT) at the Central Office (CO)
ii. Number of Optical Network Terminals (ONTs)at customer premises
• Enormous information carrying capacity
• Easily upgradeable
• Ease of installation
• Reduced O&M costs
• Long distance reach
• Immune to electromagnetic noise
• Best suited for triple play services
• Evolutionary technology based upon BPON(Broadband
passive optical network).
• It supports higher rates, enhanced security, and choice of
Layer 2 protocol (ATM, GEM, Ethernet).
• GPON uses IP-based protocols to transfer data.
• Standardized by ITU-T G.984 .
• Operates at 2.488 Gbps downstream and 1.244 Gbps
• Practical fiber split ratios up to 1:64 (standard supports up to
• Distance between OLT and ONT/ONU can be up to 20 km.
• GPON specifies QoS and management protocols required
for triple-play services over the network.
• Downstream security guaranteed with 128-bit AES
• Reduced equipment and fiber at the central office
• GPON adopts Wavelength Division Multiplexing (WDM)
technology, facilitating bi-direction communication over
a single fiber.
• To separate upstream/downstream signals of multiple
users over a single fiber
• GPON adopts two multiplexing mechanisms:
i. In downstream direction, data packets are transmitted in a broadcast
ii. In upstream direction, data packets are transmitted in a TDMA manner.
• Line rate.
i. Downstream : 2.488 Gb/s
ii. Upstream : 1.244 Gb/s.
• Broadcast mode
i. Continuous mode operation.
ii. Traffic in the downstream is sent to/received by every ONU.
i. Data confidentiality
ii. AES-Advanced Encryption Standard used for link layer encryption.
• TDMA(Time Division Multiple Access)
i. Burst mode operation.
ii. The OLT controls which ONU gets access to the upstream at a particular
moment in time.
i. Potential collision
ii. Access granting.
iii. Distance ranging.