Fronthaul network units and methods therein for synchronization over a single optical fiber in a frontahul network

1 . A method performed by a second fronthaul network unit for enabling synchronization with a first fronthaul network unit over a first single optical fiber in a fronthaul network, the method comprising:

receiving a first optical signal on the first single optical fiber;

separating the received first optical signal into a second optical signal carrying downlink (DL) radio data traffic having a first optical wavelength and a third optical signal carrying packet-based synchronization messages having a second optical wavelength, wherein the second optical wavelength is different from the first optical wavelength;

outputting the separated second optical signal towards a first optical port in the second fronthaul network unit;

splitting the separated third optical signal towards a second optical port in the second fronthaul network unit;

receiving DL radio data traffic in the separated second optical signal via the first optical port, and packet-based synchronization messages in the separated third optical signal via the second optical port;

transmitting DL radio data traffic not intended for the second fronthaul network unit using a third optical port that outputs a fourth optical signal having a third optical wavelength; and

multiplexing the fourth optical signal from the third optical port and the separated third optical signal onto a second single optical fiber.

2 . The method according to claim 1 , further comprising

receiving a fifth optical signal on the second single optical fiber;

separating the received fifth optical signal into a sixth optical signal carrying uplink (UL) radio data traffic having a fourth optical wavelength and a seventh optical signal carrying packet-based synchronization messages having a fifth optical wavelength, wherein the fourth optical wavelength is different from the fifth optical wavelength; and

outputting the separated sixth optical signal towards the third optical port in the second fronthaul network unit.

3 . The method according to claim 2 , further comprising

transmitting uplink (UL) radio data traffic to the first fronthaul network unit using the first optical port that outputs a ninth optical signal having a sixth optical wavelength.

4 . The method according to claim 3 , further comprising

transmitting packet-based synchronization messages to the first fronthaul network unit using the second optical port that outputs an eighth optical signal having the fifth optical wavelength, wherein the fifth optical wavelength is different from the sixth optical wavelength; and

multiplexing the ninth optical signal from the first optical port and the eighth optical signal from the second optical port onto the first single optical fiber towards the first fronthaul network unit.

5 . The method according to claim 4 , further comprising

multiplexing the ninth optical signal from the first optical port and the separated seventh optical signal onto the first single optical fiber towards the first fronthaul network unit.

6 . The method according to claim 2 , wherein the second optical wavelength is the same wavelength as the fifth optical wavelength, and wherein the first optical wavelength is the same wavelength as one or more of the third optical wavelength, the fourth optical wavelength, and the sixth optical wavelength.

7 . The method according to claim 2 , wherein the fifth optical wavelength is an optical wavelength that is dedicated to and uniquely emitted by the second fronthaul network unit in the fronthaul network.

8 . A second fronthaul network unit for enabling synchronization with a first fronthaul network unit over a first single optical fiber in a fronthaul network, the second fronthaul network unit being configured to:

receive a first optical signal on the first single optical fiber,

separate the received first optical signal into a second optical signal carrying downlink (DL) radio data traffic having a first optical wavelength and a third optical signal carrying packet-based synchronization messages having a second optical wavelength, wherein the second optical wavelength is different from the first optical wavelength,

output the separated second optical signal towards a first optical port in the second fronthaul network unit,

split the separated third optical signal towards a second optical port in the second fronthaul network unit,

receive DL radio data traffic in the separated second optical signal via the first optical port, and packet-based synchronization messages in the separated third optical signal via the second optical port,

transmit DL radio data traffic not intended for the second fronthaul network unit using a third optical port that outputs a fourth optical signal having a third optical wavelength, and

multiplex the fourth optical signal from the third optical port and the separated third optical signal onto a second single optical fiber.

9 . The second fronthaul network unit according to claim 8 , comprising:

an RF processing unit of a wireless communications network,

a switch or router comprising the first optical port, the second optical port, and

the third optical port;

a first and a second passive optical filter; and

an optical splitter.

10 . The second fronthaul network unit according to claim 8 , further configured to receive a fifth optical signal on the second single optical fiber, separate the received fifth optical signal into a sixth optical signal carrying uplink (UL) radio data traffic having a fourth optical wavelength and a seventh optical signal carrying packet-based synchronization messages having a fifth optical wavelength, wherein the fourth optical wavelength is different from the fifth optical wavelength, and output the separated sixth optical signal towards the third optical port in the second fronthaul network unit.

11 . The second fronthaul network unit according to claim 10 , further configured to transmit uplink (UL) radio data traffic to the first fronthaul network unit using the first optical port that outputs a ninth optical signal having a sixth optical wavelength.

12 . The second fronthaul network unit according to claim 11 , further configured to transmit packet-based synchronization messages to the first fronthaul network unit using the second optical port that outputs an eighth optical signal having the fifth optical wavelength, wherein the fifth optical wavelength is different from the sixth optical wavelength, and multiplex the ninth optical signal from the first optical port and the eighth optical signal from the second optical port onto the first single optical fiber towards the first fronthaul network unit.

13 . The second fronthaul network unit according to claim 11 , further configured to multiplex the ninth optical signal from the first optical port and the separated seventh optical signal onto the first single optical fiber towards the first fronthaul network unit.

14 . The second fronthaul network unit according to claim 10 , wherein the second optical wavelength is the same wavelength as the fifth optical wavelength, and wherein the first optical wavelength is the same wavelength as one or more of the third optical wavelength, the fourth optical wavelength, and the sixth optical wavelength.

15 . The second fronthaul network unit according to claim 10 , wherein the fifth optical wavelength is an optical wavelength that is dedicated to and uniquely emitted by the second fronthaul network unit in the fronthaul network.

16 . A method performed by a first fronthaul network unit for enabling synchronization with at least two second fronthaul network units over a first single optical fiber in a fronthaul network, the method comprising:

transmitting downlink (DL) radio data traffic intended for one or more of the at least two second fronthaul network units using a first optical port that outputs a first optical signal having a first optical wavelength;

transmitting packet-based synchronization messages to the at least two second fronthaul network units using a second optical port that outputs a second optical signal having a second optical wavelength, wherein the second optical wavelength is different from the first optical wavelength;

multiplexing the first optical signal from the first optical port and the second optical signal from the second optical port onto the same single optical fiber towards the at least two second fronthaul network units; and

allocating a respective uplink time slot to each of the at least two second fronthaul network units for transmitting uplink synchronization messages on the second optical wavelength.